EXHIBIT B
                      AGREEMENT AND PLAN OF REORGANIZATION
         THIS  AGREEMENT  AND  PLAN OF  REORGANIZATION  is made as of the day of
January, 1996, by and between Pioneer Three, a Massachusetts business trust (the
"Current  Fund"),  and Pioneer Mid-Cap Growth Fund, a business trust duly formed
under the laws of the State of Delaware (the "Successor Trust").
         This  Agreement  is  intended  to  be  and  is  adopted  as a  plan  of
reorganization  within the  meaning of Section  368 (a)(1) of the U.S.  Internal
Revenue  Code of 1986,  as amended (the  "Code"),  and is intended to effect the
reorganization  (a  "reorganization")  of the Current  Fund,  as a new  separate
series of the Successor Trust. The  reorganization  will involve the transfer of
all of the assets of the Current Fund to the sole series of the Successor  Trust
(the  "Successor  Fund") solely in exchange for (1)  assumption by the Successor
Fund of all  liabilities  of the Current  Fund and (2) the issuance of shares of
beneficial interest (the "Successor Shares") by the Successor Trust on behalf of
the Successor Fund to the Current Fund, followed by the pro rata distribution on
the Closing Date (as defined  below) of the  Successor  Shares to the holders of
shares  of   beneficial   interest  of  the  Current  Fund  (the  "Current  Fund
Shareholders")  in exchange for their shares of the Current Fund in  liquidation
and  termination  of the  Current  Fund,  all  upon  the  terms  and  conditions
hereinafter set forth in this Agreement.
         In  consideration  of the premises and of the covenants and  agreements
hereinafter set forth the parties hereto covenant and agree as follows.
1.       TRANSFER OF ASSETS OF THE CURRENT  FUND IN EXCHANGE FOR  ASSUMPTION  OF
         LIABILITIES  AND ISSUANCE OF SUCCESSOR  SHARES OF THE SUCCESSOR  TRUST;
         TERMINATION OF THE CURRENT FUND
         1.1  Subject to the terms and  conditions  set forth  herein and on the
basis of the representations  and warranties  contained herein, the Current Fund
agrees  to  transfer  all of the  assets  of the  Current  Fund as set  forth in
paragraph  1.2 and assign and transfer all of its  liabilities  to the Successor
Fund of the Successor Trust which has been established solely for the purpose of
acquiring all of the assets and assuming all of the  liabilities  of the Current
Fund. The Successor Trust has not issued any Shares or commenced operations. The
Successor  Trust on behalf of the Successor Fund agrees that in exchange for all
of the assets of the Current Fund (1) the Successor Fund shall assume all of the
liabilities of the Current Fund, whether contingent or otherwise, then existing,
and further (2) the Successor Trust shall deliver to the Current Fund the number
of full and fractional  Successor Shares equal to the value of the assets of the
Current Fund  transferred to the Successor  Fund,  minus the  liabilities of the
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Current Fund assumed by the Successor Fund (the "Net  Assets"),  as described in
paragraph  3.1  on  the  Closing  Date  provided  for  in  paragraph  3.1.  Such
transactions shall take place at the Closing provided for in paragraph 3.1.
         1.2 The assets of the Current Fund to be acquired by the Successor Fund
shall include,  without  limitation,  all cash,  cash  equivalents,  securities,
receivables (including interest and dividends receivable),  any claims or rights
of action or rights to register  shares under  applicable  securities  laws, any
books or records of the  Current  Fund and other  property  owned by the Current
Fund and any  deferred or prepaid  expenses  shown as assets on the books of the
Current Fund on the Closing Date provided for in paragraph 3.1.
         1.3 Immediately upon delivery to the Current Fund of Successor  Shares,
any duly authorized officer of the Current Fund shall cause the Current Fund, as
the then sole shareholder of the Successor Fund, to (i) elect as Trustees of the
Successor Trust the persons who currently serve as Trustees of the Current Fund;
(ii) ratify the  selection  of the  independent  accountants;  (iii)  approve an
investment  advisory  agreement  for the  Successor  Fund in the form  currently
approved by the shareholders of the Current Fund; (iv) approve a Rule 12b-1 plan
in the form  currently in place with respect to the Current Fund; and (v) adopt,
on behalf of the Successor Fund, the investment objectives,  investment policies
and investment restrictions of the Current Fund.
         1.4 As provided in paragraph  3.4, on the Closing Date the Current Fund
will  distribute in liquidation  the Successor  Shares pro rata in proportion to
the Current Fund's respective shares of beneficial  interest in the Current Fund
("Current Fund Shares") to Current Fund  Shareholders of record determined as of
the close of business  on the Closing  Date,  in exchange  for the Current  Fund
Shares.  Such distribution will be accomplished by the transfer of the Successor
Shares then  credited to the account of the Current Fund on the share records of
the  Successor  Trust to open  accounts  on those  records  in the  names of the
Current Fund Shareholders and representing the respective pro rata number of the
Successor  Shares  received from the Successor  Trust on behalf of the Successor
Fund due the Current  Fund  Shareholders.  The  Successor  Trust shall not issue
certificates representing Successor Shares in connection with such distribution.
Fractional  Successor  Shares  shall be  rounded  to the third  place  after the
decimal point.
         1.5 As soon as  practicable  after the  distribution  of the  Successor
Shares as set forth in Section 1.4, the Current Fund shall be terminated and any
such further  actions shall be taken in connection  therewith as are required by
applicable law.
         1.6  Ownership  of  the  Successor   Shares  of  each   Successor  Fund
Shareholder shall be maintained  separately on the books of Pioneering  Services
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Corporation as the Successor Trust's shareholder services and transfer agent.
         1.7 Any transfer  taxes payable upon issuance of Successor  Shares in a
name other than the registered holder of the Current Fund Shares on the books of
the  Current  Fund as of that  time  shall be paid by the  person  to whom  such
Successor Shares are to be distributed as a condition of such transfer.
2.       VALUATION
         2.1 The value of the  Current  Fund's Net Assets to be  acquired by the
Successor Trust on behalf of the Successor Fund hereunder shall be the net asset
value  computed  as of  the  valuation  time  provided  in  the  Current  Fund's
prospectus on the Closing Date using the valuation  procedures  set forth in the
Current Fund's current prospectus or statement of additional information.
         2.2 The value of full and fractional  Successor  Shares to be issued in
exchange  for the Current  Fund's Net Assets  shall be equal to the value of the
Net  Assets of the  Current  Fund on the  Closing  Date,  and the number of such
Successor  Shares  shall equal the number of full and  fractional  Current  Fund
Shares of the Current Fund on the Closing Date.
         2.3 All computations of value shall be made by ▇▇▇▇▇ Brothers  ▇▇▇▇▇▇▇▇
& Co. as custodian for the Current Fund and the Successor Trust.
3.       CLOSING AND CLOSING DATE
         3.1 The  transfer of the  Current  Fund's  assets in  exchange  for the
assumption  by the  Successor  Fund of the Current  Fund's  liabilities  and the
issuance of Successor Shares to the Current Fund, as described  above,  together
with related acts necessary to consummate such acts (the "Closing"), shall occur
at the offices of ▇▇▇▇ and ▇▇▇▇ at ▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇▇,  ▇▇▇▇▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇
on January __, 1996 ("Closing Date"), or at such other place or date on or prior
to March 31, 1996 as the parties may agree in writing.  All acts taking place at
the Closing  shall be deemed to take place  simultaneously  as of the last daily
determination  of the net asset value of any Current  Fund or at such other time
and/or place as the parties may agree.
         3.2 In the  event  that on the  Closing  Date  (a) the New  York  Stock
Exchange is closed to trading or trading thereon is restricted or (b) trading or
reporting  of  trading  on said  Exchange  or in any  market in which  portfolio
securities  of any  Current  Fund  are  traded  is  disrupted  so that  accurate
appraisal  of  the  value  of the  total  net  assets  of the  Current  Fund  is
impracticable,  the Closing shall be postponed until the first business day upon
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which  trading  shall  have been fully  resumed  and  reporting  shall have been
restored.
         3.3 The  Current  Fund shall  deliver at the Closing a  certificate  or
separate  certificates of an authorized officer stating that it has notified the
Custodian,   as  custodian  for  the  Current   Fund,  of  the  Current   Fund's
reorganization as the Successor Fund.
         3.4  Pioneering  Services  Corporation,  as  shareholder  services  and
transfer agent for the Current Fund,  shall deliver at the Closing a certificate
as to the  conversion  on its books and records of the Current Fund  Shareholder
account to an account as a holder of Successor Shares. The Successor Trust shall
issue and deliver to the Current Fund a  confirmation  evidencing  the Successor
Shares to be credited on the Closing Date or provide  evidence  satisfactory  to
the Current Fund that such  Successor  Shares have been  credited to the Current
Fund's  account on the books of the Successor  Trust.  At the Closing each party
shall  deliver  to the other  such  bills of sale,  checks,  assignments,  stock
certificates, receipts or other documents as such other party or its counsel may
reasonably request.
         3.5 Portfolio  securities  that are not held in book-entry  form in the
name of the  Custodian as record  holder for the Current Fund shall be presented
by the Current Fund to the Custodian for examination no later than five business
days  preceding the Closing  Date.  Portfolio  securities  which are not held in
book-entry  form shall be delivered by the Current Fund to the Custodian for the
account of the Successor Fund on the Closing Date,  duly endorsed in proper form
for  transfer,  in such  condition as to  constitute  good  delivery  thereof in
accordance with the custom of brokers, and shall be accompanied by all necessary
federal and state stock transfer stamps or a check for the appropriate  purchase
price  thereof.  Portfolio  securities  held  of  record  by  the  Custodian  in
book-entry  form on  behalf  of the  Current  Fund  shall  be  delivered  to the
Successor  Fund  by the  Custodian  by  recording  the  transfer  of  beneficial
ownership  thereof on its records.  The cash  delivered  shall be in the form of
currency or by the Custodian  crediting the Successor  Fund' account  maintained
with the Custodian with immediately available funds.
4.       REPRESENTATIONS AND WARRANTIES
         4.1 The Current Fund represents and warrants as follows:
             4.1.A. The Current Fund is a business trust duly organized, validly
existing  and  in  good  standing  under  the  laws  of  The   Commonwealth   of
Massachusetts  and has the power to own all of its  properties  and assets  and,
subject to approval by the  shareholders  of the  Current  Fund,  to perform its
obligations under this Agreement. The Current Fund is not required to qualify to
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do business in any jurisdiction in which it is not so qualified or where failure
to qualify  would not subject it to any material  liability or  disability.  The
Current Fund has all necessary  federal,  state and local  authorizations to own
all of its  properties  and  assets  and to carry on its  business  as now being
conducted;
             4.1.B.  The  Current  Fund  is  a  registered   investment  company
classified  as a management  company of the open-end  type and its  registration
with the Securities and Exchange  Commission (the "Commission") as an investment
company under the  Investment  Company Act of 1940, as amended (the "1940 Act"),
is in full force and effect;
             4.1.C.  The Current  Fund is not, and the  execution,  delivery and
performance of this Agreement will not result,  in violation of any provision of
its Declaration of Trust or By-laws,  or any agreement,  indenture,  instrument,
contract,  lease or other undertaking to which the Current Fund is a party or by
which the Current Fund is bound;
             4.1.D.  The  Current  Fund  has  no  material  contracts  or  other
commitments (other than this Agreement or agreements on behalf of a Current Fund
for the purchase of securities  entered into in the ordinary  course of business
and  consistent  with its  obligations  under this  Agreement)  that will not be
terminated  without  liability  to the  Current  Fund on or prior to the Closing
Date;
             4.1.E.  No material  litigation  or  administrative  proceeding  or
investigation  of or before any court or governmental  body presently is pending
or threatened  against the Current Fund or any of its properties or assets.  The
Current Fund knows of no facts that might form the basis for the  institution of
such  proceedings  and the  Current  Fund is not a party to, or subject  to, the
provisions of any order,  decree or judgment of any court or  governmental  body
that materially and adversely  affects its business or its ability to consummate
the transactions herein contemplated;
             4.1.F.  At the date hereof and at the Closing  Date,  all  federal,
state and other tax returns and reports, including information returns and payee
statements,  of the Current Fund required by law to have been filed or furnished
by such dates  shall have been filed or  furnished  and all  federal,  state and
other  taxes,  interest  and  penalties  shall  have  been paid so far as due or
provision  shall have been made for the  payment  thereof  and no such return is
currently under audit and no assessment has been asserted with respect to any of
such returns or reports;
             4.1.G.  The  Current  Fund has elected to be treated as a regulated
investment  company  under  Subchapter M of the Code,  has qualified as such for
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each  taxable  year  since its  inception,  and will  qualify  as such as of the
Closing Date;
             4.1.H.  The  authorized  capital of the Current Fund consists of an
unlimited  number of shares of beneficial  interest.  All issued and outstanding
shares of  beneficial  interest of the Current Fund are, and at the Closing Date
will be, duly and validly issued and outstanding,  fully paid and nonassessable.
The Current Fund does not have outstanding any options, warrants or other rights
to subscribe  for or purchase any of its shares of beneficial  interest,  nor is
there outstanding any security  convertible into any of its shares of beneficial
interest;
             4.1.I.  The information to be furnished by the Current Fund for use
in applications for orders,  registration statements,  proxy materials and other
documents   which  may  be  necessary  in  connection   with  the   transactions
contemplated  hereby  shall be accurate  and  complete  and shall  comply in all
material  respects  with  federal  securities  and  other  laws and  regulations
thereunder applicable thereto;
             4.1.J.  All of the issued and outstanding  Current Fund Shares will
at the  time of the  Closing  be  held  by the  persons  and in the  amounts  as
certified in accordance with the provisions of paragraph 3.4;
             4.1.K.  At the Closing  Date,  the Current  Fund will have good and
marketable  title to the assets to be transferred to the Successor Fund pursuant
to paragraph 1.1, and full right, power and authority to sell, assign,  transfer
and deliver  such assets  hereunder,  and upon  delivery and in payment for such
assets,  the  Successor  Fund will acquire  good and  marketable  title  thereto
subject  to no  restrictions  on  the  full  transfer  thereof,  including  such
restrictions as might arise under the Securities Act of 1933, as amended;
             4.1.L.  The execution,  delivery and  performance of this Agreement
will have been duly authorized prior to the Closing Date by all necessary action
on the part of the  Current  Fund and this  Agreement  constitutes  a valid  and
binding obligation of the Current Fund enforceable in accordance with its terms,
subject to the approval of the Current Fund's Shareholders; and
             4.1.M. No consent, approval, authorization or order of any court or
governmental  authority is required for the  consummation by the Current Fund of
the transactions  contemplated  herein,  except such as shall have been obtained
prior to the Closing Date.
         4.2 The Successor Trust represents and warrants as follows:
             4.2.A.  The  Successor  Trust is a business  trust duly  organized,
validly  existing and in good  standing  under the laws of the State of Delaware
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and has the power to own all of its  properties  and assets  and to perform  its
obligations under this Agreement; the Successor Trust is not required to qualify
to do  business in any  jurisdiction  in which it is not so  qualified  or where
failure to qualify would not subject it to any material liability or disability;
the Successor Trust has all necessary federal, state and local authorizations to
own all of its  properties  and assets and to carry on its business as now being
conducted;  that as of the date hereof and as of the Closing Date, the Successor
Fund is the only series of the Successor Trust; and the Successor Fund is a duly
established and designated series of the Successor Trust;
             4.2.B. The Successor Trust is not, and the execution,  delivery and
performance of this Agreement will not result,  in violation of any provision of
the  Declaration  of Trust or By-laws of the Successor  Trust or any  agreement,
indenture,  instrument,  contract,  lease or  other  undertaking  to  which  the
Successor Trust is a party or by which the Successor Trust is bound;
             4.2.C.  No material  litigation  or  administrative  proceeding  or
investigation of or before any court or governmental  body is presently  pending
or threatened  against the Successor  Trust or any of its  properties or assets.
The  Successor  Trust  knows of no facts  that  might  form  the  basis  for the
institution of such  proceedings,  and the Successor Trust is not a party to, or
subject  to, the  provisions  of any order,  decree or  judgment of any court or
governmental  body that  materially  and  adversely  affects its business or its
ability to consummate the transactions herein contemplated;
             4.2.D. The Successor Trust will cause the Successor Fund to qualify
as a regulated investment company under subchapter M of the Code for the taxable
year in which the  Closing  occurs and to  continue  to qualify as such for each
taxable year;
             4.2.E.  Prior to the  Closing  Date,  there  shall be no issued and
outstanding  Successor  Shares or any other  securities of the Successor  Trust;
Successor Shares issued in connection with the transactions  contemplated herein
will be duly  and  validly  issued  and  outstanding  and  fully  paid  and non-
assessable;
             4.2.F.  The execution,  delivery and  performance of this Agreement
has been duly  authorized by all  necessary  action on the part of the Successor
Trust,  and this  Agreement  constitutes  a valid and binding  obligation of the
Successor Trust  enforceable  against the Successor Trust in accordance with its
terms;
             4.2.G.  The  information to be furnished by the Successor Trust for
use in applications  for orders,  registration  statements,  proxy materials and
other  documents  which may be necessary  in  connection  with the  transactions
contemplated  hereby  shall be accurate  and  complete  and shall  comply in all
                                      B-7
material  respects  with  Federal  securities  and  other  laws and  regulations
applicable thereto; and
                  4.2.H.  No consent,  approval,  authorization  or order of any
court  or  governmental  authority  is  required  for  the  consummation  by the
Successor Trust of the transactions  contemplated  herein,  except such as shall
have been obtained prior to the Closing Date.
5.       COVENANTS OF THE CURRENT FUND AND THE SUCCESSOR TRUST
         5.1 The Current Fund covenants that the Successor  Shares are not being
acquired  for the  purpose of making  any  distribution  thereof,  other than in
accordance with the terms of this Agreement.
         5.2 The Current Fund covenants that it will assist the Successor  Trust
in  obtaining  such  information  as the  Successor  Trust  reasonably  requests
concerning the beneficial ownership of Current Fund Shares.
         5.3 The Current Fund will,  from time to time, as and when requested by
the Successor Trust execute and deliver,  or cause to be executed and delivered,
all such assignments and other  instruments,  and will take or cause to be taken
such further  action,  as the Successor Trust may deem necessary or desirable in
order to vest in, and confirm to, the Successor  Fund,  title to, and possession
of, all the assets of the Current  Fund to be sold,  assigned,  transferred  and
delivered  hereunder  and  otherwise to carry out the intent and purpose of this
Agreement.
         5.4 The Successor  Trust will, from time to time, as and when requested
by the Current  Fund,  execute and deliver or cause to be executed and delivered
all such assignments and other  instruments,  and will take or cause to be taken
such  further  action,  as the Current  Fund may deem  necessary or desirable in
order to vest in, and  confirm to, the  Current  Fund,  on behalf of the Current
Funds, title to, and possession of, the Successor Shares issued, sold, assigned,
transferred  and  delivered  hereunder and otherwise to carry out the intent and
purpose of this Agreement.
         5.5 The Successor Trust shall use all reasonable  efforts to obtain the
approvals  and  authorizations  required by the 1933 Act,  the 1940 Act and such
state  securities laws as it may deem  appropriate in order to operate after the
Closing Date.
         5.6 Subject to the provisions of this  Agreement,  the Successor  Trust
and the Current Fund each will take,  or cause to be taken,  all action and will
do or cause to be done all things reasonably  necessary,  proper or advisable to
consummate and make effective the transactions contemplated by this Agreement.
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         5.7 As promptly as  practicable,  but in any event within 60 days after
the Closing Date, the Current Fund shall furnish to the Successor Trust, in such
form as is reasonably  satisfactory  to the Successor  Trust, a statement of the
earnings and profits of the Current Fund for federal income tax purposes, and of
any capital  loss  carryovers  and other items that will be carried  over to the
Successor Fund as a result of Section 381 of the Code, and which  statement will
be certified by the President or Treasurer of the Current Fund.
6.       CONDITIONS PRECEDENT TO OBLIGATIONS OF THE CURRENT FUND
         The  obligations  of the Current Fund to  consummate  the  transactions
provided for herein shall be subject to the  performance by the Successor  Trust
of all the  obligations to be performed by the Successor  Trust  hereunder on or
before the Closing  Date and,  in addition  thereto,  to the  following  further
conditions:
         6.1 All representations and warranties of the Successor Trust contained
in this Agreement  shall be true and correct in all material  respects as of the
date hereof except as they may be affected by the  transactions  contemplated by
this  Agreement,  as of the Closing  Date,  with the same force and effect as if
made on and as of the Closing Date; and
         6.2 The Successor Trust shall have delivered on the Closing Date to the
Current  Fund a  certificate  executed  in the  Successor  Trust's  name  by its
President or Vice President,  in form and substance  satisfactory to the Current
Fund, dated as of the Closing Date, to the effect that the  representations  and
warranties of the Successor Trust made in this Agreement are true and correct at
and as of the Closing Date,  except as they may be affected by the  transactions
contemplated by this Agreement, and as to such other matters as the Current Fund
shall reasonably request.
Each of the foregoing conditions precedent may be waived by the Current Fund.
7.       CONDITIONS PRECEDENT TO OBLIGATIONS OF THE SUCCESSOR TRUST
         The obligations of the Successor  Trust to consummate the  transactions
provided for herein shall be subject to the  performance  by the Current Fund of
all the  obligations  to be performed by the Current Fund hereunder on or before
the Closing Date and, in addition thereto, to the following further conditions:
         7.1 All representations and warranties of the Current Fund contained in
this Agreement shall be true and correct in all material respects as of the date
hereof and, except as they may be affected by the  transactions  contemplated by
this  Agreement,  as of the Closing  Date,  with the same force and effect as if
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made on and as of the Closing Date;
         7.2 The Current Fund shall have delivered to the Successor Trust on the
Closing Date a statement of the Current Fund's assets and liabilities,  prepared
in  accordance  with  generally  accepted  accounting  principles   consistently
applied,  together with a certificate of the Treasurer or Assistant Treasurer of
the Current Fund as to its portfolio  securities  and the Current Fund's federal
income tax basis and holding period for each such  portfolio  security as of the
Closing Date; and
         7.3 The Current Fund shall have delivered to the Successor Trust on the
Closing Date a certificate  executed in the Current Fund's name by its President
or Vice President,  in form and substance  satisfactory to the Successor  Trust,
dated  as of the  Closing  Date,  to the  effect  that the  representations  and
warranties  of the Current Fund made in this  Agreement  are true and correct at
and as of the Closing Date,  except as they may be affected by the  transactions
contemplated  by this  Agreement,  and as to such other matters as the Successor
Trust shall reasonably request.
         Each  of  the  foregoing  conditions  precedent  may be  waived  by the
Successor Trust.
8.       FURTHER CONDITIONS PRECEDENT TO OBLIGATIONS OF THE CURRENT FUND AND THE
         SUCCESSOR TRUST
         The  obligations  of the Current Fund and the Successor  Trust are each
subject to the further conditions that on or before the Closing Date:
         8.1 This Agreement and the transactions  contemplated herein shall have
been  approved by the  requisite  vote of the  Current  Fund's  Shareholders  in
accordance with applicable law;
         8.2 On the Closing Date, no action,  suit or other  proceeding shall be
pending  before  any  court or  governmental  agency  in which it is  sought  to
restrain or prohibit or to obtain  damages or other relief in  connection  with,
the transactions contemplated hereby;
         8.3 All consents of other  parties and all other  consents,  orders and
permits of federal,  state and local regulatory  authorities (including those of
the  Commission and of state  securities  authorities)  deemed  necessary by the
Successor  Trust or the Current  Fund to permit  consummation,  in all  material
respects,  of the  transactions  contemplated  hereby shall have been  obtained,
except  where  failure to obtain  any such  consent,  order or permit  would not
involve a risk of a material  adverse  effect on the assets or properties of the
Successor  Trust or the Current Fund,  provided that either party hereto may for
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itself waive any of such conditions;
         8.4 The  President  of the  Successor  Trust  shall  have  delivered  a
certificate  to the  Current  Fund  on the  Closing  Date  certifying  that  the
Successor Trust has taken all necessary  action so that it shall be a registered
open-end investment company under the 1940 Act; and
         8.5 The Current Fund and the Successor  Trust shall have received on or
before the Closing Date an opinion of ▇▇▇▇ and ▇▇▇▇  satisfactory to the Current
Fund and the Successor Trust,  substantially to the effect that, with respect to
the Current Fund, for federal income tax purposes:
                  8.5.A.  The acquisition of all of the assets of a Current Fund
         by the Successor  Fund solely in exchange for the issuance of Successor
         Shares to the Current Fund and the  assumption by the Successor Fund of
         all  of  the   liabilities  of  the  Current  Fund,   followed  by  the
         distribution  in  liquidation  by the  Current  Fund of such  Successor
         Shares to the Current Fund  Shareholders  in exchange for their Current
         Fund Shares and the  termination of the Current Fund, will constitute a
         reorganization within the meaning of Section 368(a)(1) of the Code, and
         the  Current  Fund and the  Successor  Fund  will each be "a party to a
         reorganization" within the meaning of Section 368(b) of the Code;
                  8.5.B.  No gain or loss will be recognized by the Current Fund
         upon (i) the transfer of all of its assets to the Successor Fund solely
         in exchange for the  issuance of  Successor  Shares to the Current Fund
         and  the  assumption  by  the  Successor  Fund  of the  Current  Fund's
         liabilities  and  (ii)  the  distribution  by the  Current  Fund of the
         Successor Shares to the Current Fund Shareholders;
                  8.5.C.  No gain or loss will be  recognized  by any  Successor
         Fund upon its receipt of all of the  Current  Fund's  assets  solely in
         exchange for the issuance of the  Successor  Shares to the Current Fund
         and the assumption by the Successor  Fund of all of the  liabilities of
         the Current Fund;
                  8.5.D.  The tax basis of the assets  acquired  by a  Successor
         Fund from the  Current  Fund will be the same as the tax basis of those
         assets in the Current Fund's hands immediately before the transfer;
                  8.5.E.  The tax  holding  period of the assets of the  Current
         Fund in the hands of the Successor Fund will include the Current Fund's
         tax holding period for those assets;
                                      B-11
                  8.5.F. The Current Fund's Shareholders will not recognize gain
         or loss upon the exchange of all of their  Current  Fund Shares  solely
         for Successor Shares as part of the transaction;
                  8.5.G.  The tax  basis of the  Successor  Shares  received  by
         Current  Fund  Shareholders  in  the  transaction  will  be,  for  each
         shareholder,  the same as the tax  basis  of the  Current  Fund  Shares
         surrendered in exchange therefor; and
                  8.5.H. The tax holding period of the Successor Shares received
         by Current Fund Shareholders  will include,  for each such Shareholder,
         the tax holding  period for the  Current  Fund  Shares  surrendered  in
         exchange  therefor,  provided that the Current Fund Shares were held as
         capital assets on the date of the exchange.
The  Current  Fund  and   Successor   Trust  each  agree  to  make  and  provide
representations  with respect to the Current Fund and the  Successor  Fund which
are  reasonably  necessary  to  enable  ▇▇▇▇  and  ▇▇▇▇ to  deliver  an  opinion
substantially as set forth in this paragraph 8.5, which opinion may address such
other federal income tax  consequences,  if any, as ▇▇▇▇ and ▇▇▇▇ believes to be
material to the transaction.
         Each of the  foregoing  conditions  precedent to the  obligations  of a
party,  except  for the  receipt  of the  opinion  of ▇▇▇▇ and ▇▇▇▇ set forth in
paragraph 8.5, may be waived by that party.
9.       BROKERAGE FEES AND EXPENSES
         9.1 The Successor Trust and the Current Fund each represent and warrant
to the other that there are no broker's or finder's  fees payable in  connection
with the transactions contemplated hereby.
         9.2 The Current  Fund and the  Successor  Fund shall each be liable for
its own expenses  incurred in connection with entering into and carrying out the
provisions of this Agreement whether or not the transactions contemplated hereby
are  consummated;  if the  transactions  are  consummated,  such expenses of the
Current Fund will be assumed by the Successor Fund as part of the transactions.
10.      ENTIRE AGREEMENT
         The  Successor  Trust and the Current Fund agree that neither party has
made any representation, warranty or covenant not set forth herein and that this
Agreement   constitutes   the  entire   agreement   between  the  parties.   The
representations,  warranties and covenants  contained  herein or in any document
delivered   pursuant  hereto  or  in  connection   herewith  shall  survive  the
consummation of the transactions contemplated hereunder.
                                      B-12
11.      TERMINATION
         11.1 This  Agreement may be  terminated by the mutual  agreement of the
Successor Trust and the Current Fund. In addition, either the Successor Trust or
the Current Fund may at its option  terminate  this Agreement at or prior to the
Closing Date because:
                  11.1.A.  There exists a material  breach by the other party of
         any  representations,  warranties or agreements  contained herein to be
         performed at or prior to the Closing Date; or
                  11.1.B.  A condition  herein  expressed to be precedent to the
         obligations of the terminating party has not been met and it reasonably
         appears that it will not or cannot be met.
         11.2 In the event of any such termination,  there shall be no liability
for damages on the part of the  Successor  Trust or the Current  Fund,  or their
respective trustees,  directors or officers, to the other party or its trustees,
directors or officers.
12.      AMENDMENT
         This Agreement may be amended,  modified or supplemented in such manner
as may be mutually  agreed upon in writing by the  parties;  provided,  however,
that   following  the  approval  of  this   Agreement  by  the  Current   Funds'
Shareholders,  no such  amendment may have the effect of changing the provisions
for  determining  the number of Successor  Shares to be paid to the Current Fund
Shareholders  under  this  Agreement  to  the  detriment  of  the  Current  Fund
Shareholders without their further approval.
13.      HEADINGS; COUNTERPARTS; GOVERNING LAW; ASSIGNMENT
         13.1 The article and paragraph headings contained in this Agreement are
for  reference  purposes  only and shall not  affect in any way the  meaning  or
interpretation of this Agreement.
         13.2 This Agreement may be executed in any number of counterparts, each
of which shall be deemed an original.
         13.3 This  Agreement  shall be governed by and  construed in accordance
with the laws of The Commonwealth of Massachusetts.
         13.4 This  Agreement  shall be binding upon and inure to the benefit of
the  parties  hereto  and  their  respective  successors  and  assigns,  but  no
assignment or transfer hereof or of any rights or obligations hereunder shall be
made by any party without the written consent of the other party. Nothing herein
expressed  or implied is intended or shall be  construed  to confer upon or give
any  person,  firm or  corporation  other  than the  parties  hereto  and  their
                                      B-13
respective  successors  and assigns any rights or remedies under or by reason of
this Agreement.
         13.5 All persons  dealing with the Successor  Trust must look solely to
the property of the Successor  Trust for the  enforcement  of any claims against
the Successor Trust as neither the Trustees,  officers,  agents nor shareholders
of the Successor  Trust assume any personal  liability for  obligations  entered
into on behalf of the Successor  Trust.  No other series of the of the Successor
Trust hereafter  established shall be responsible for any obligations assumed by
the Successor Trust on behalf of the Successor Fund under this Agreement.
         13.6 A copy of the  Agreement and  Declaration  of Trust of the Current
Fund  is  on  file  with  the  Secretary  of  State  of  The   Commonwealth   of
Massachusetts,  and notice is hereby given that this  instrument  is executed on
behalf of the Trustees of the Current Fund as trustees and not  individually and
that  the  obligations  of this  instrument  are  not  binding  upon  any of the
trustees,  officers,  or shareholders of the Current Fund individually,  but are
binding only upon the assets and property of the Current Fund.
14.      NOTICES
         Any notice,  report,  statement or demand  required or permitted by any
provisions of this  Agreement  shall be in writing and shall be given by prepaid
telegraph,  telecopy or  certified  mail  addressed  to the Current  Fund or the
Successor  Trust,  each  at  ▇▇  ▇▇▇▇▇  ▇▇▇▇▇▇,  ▇▇▇▇▇▇,   ▇▇▇▇▇▇▇▇▇▇▇▇▇  ▇▇▇▇▇,
Attention: Secretary.
                                      B-14
         IN  WITNESS  WHEREOF,  each  of the  parties  hereto  has  caused  this
Agreement to be executed by its duly authorized officer.
                                    PIONEER THREE
                                    By:_____________________________
                                    Its:____________________________
                                         Title
                                    PIONEER    MID-CAP   GROWTH
                                    FUND,  a Delaware  business
                                    trust, on behalf of Pioneer
                                    Mid-Cap Growth Fund
                                    By:_____________________________
                                    Its:____________________________
                                         Title
                                      B-15