[LETTER ON WILMER CUTLER PICKERING HALE AND DORR LLP LETTERHEAD]

                                      DRAFT OF MARCH 16, 2005, SUBJECT TO CHANGE

_______________, 2005

John Hancock World Fund, on behalf of
John Hancock Biotechnology Fund
101 Huntington Avenue
Boston, Massachusetts 02199

John Hancock World Fund, on behalf of
John Hancock Health Sciences Fund
101 Huntington Avenue
Boston, Massachusetts 02199

Ladies and Gentlemen:

This opinion is being delivered to you in connection with the Agreement and Plan
of Reorganization  (the "Agreement") made as of __________,  2005 by and between
John  Hancock  World Fund,  a  Massachusetts  business  trust,  on behalf of its
series,  John Hancock  Biotechnology  Fund ("Acquiring  Fund"), and John Hancock
World Fund on behalf of its series, John Hancock Health Sciences Fund ("Acquired
Fund"). Pursuant to the Agreement, Acquiring Fund will acquire all of the assets
of Acquired Fund in exchange  solely for (i) the assumption by Acquiring Fund of
all of the Acquired Fund Liabilities, as defined in the Agreement (the "Acquired
Fund Liabilities"), and (ii) the issuance of Class A shares, Class B shares, and
Class C shares of beneficial  interest of Acquiring  Fund (the  "Acquiring  Fund
Shares") to Acquired  Fund,  followed by the  distribution  by Acquired Fund, in
liquidation of Acquired  Fund, of the Acquiring Fund Shares to the  shareholders
of Acquired Fund and the  termination of Acquired Fund (the  foregoing  together
constituting  the  "Transaction").  All  section  references,  unless  otherwise
indicated,  are to the United States  Internal  Revenue Code of 1986, as amended
(the "Code").

In rendering  this opinion,  we have examined and relied upon (i) the prospectus
for Acquiring Fund dated _________ (ii) the statement of additional  information
for Acquiring  Fund dated  ____________;  (iii) the prospectus for Acquired Fund
dated __________; (iv) the statement of additional information for Acquired Fund
dated  ___________;  (v) the  Notice of Meeting of  Shareholders  Scheduled  for
__________ and the accompanying proxy statement and prospectus on Form N-14 (the
"Proxy   Statement");   (vi)  the  Agreement;   (vii)  the  tax   representation
certificates  delivered  pursuant to the  Agreement and relevant to this opinion
(the  "Representation  Certificates");  and (viii)  such other  documents  as we
deemed necessary or relevant to our analysis.

In our  examination of documents,  we have assumed the  authenticity of original
documents, the accuracy of copies, the genuineness of signatures,  and the legal
capacity of  signatories.  We have assumed that all parties to the Agreement and
to any other documents examined by us have



John Hancock Biotechnology Fund
John Hancock Health Sciences Fund
__________________________, 2005
Page 2

acted,  and will  act,  in  accordance  with the  terms  of such  Agreement  and
documents and that the Transaction will be consummated pursuant to the terms and
conditions set forth in the Agreement  without the waiver or modification of any
such terms and conditions. Furthermore, we have assumed that all representations
contained in the Agreement,  as well as those  representations  contained in the
Representation  Certificates  are,  on the date  hereof,  and  will  be,  at the
consummation of the Transaction, true and complete in all material respects, and
that any representation  made in any of the documents referred to herein "to the
knowledge and belief" (or similar  qualification) of any person or party is, and
at  the   consummation  of  the  Transaction   will  be,  correct  without  such
qualification. We have also assumed that as to all matters for which a person or
entity has represented  that such person is not a party to, does not have, or is
not aware of any plan, intention,  understanding, or agreement, there is no such
plan, intention,  understanding,  or agreement.  We have not attempted to verify
independently any of the above assumptions or representations.

The conclusions  expressed  herein  represent our judgment  regarding the proper
treatment  of the  Transaction  under the income  tax laws of the United  States
based upon the Code, case law, Treasury  Regulations,  and the rulings and other
pronouncements  of the Internal Revenue Service (the "Service") in effect on the
date of this  opinion.  No  assurances  can be given  that such laws will not be
amended or otherwise  changed after the  consummation of the Transaction or that
such changes will not affect the conclusions expressed herein. Nevertheless,  we
undertake  no  responsibility  to  advise  you of  any  developments  after  the
consummation  of the  Transaction in the  application or  interpretation  of the
income tax laws of the United States.

Our opinion  represents our best judgment  regarding how a court would decide if
presented with the issues  addressed  herein and is not binding upon the Service
or any court.  Moreover,  our  opinion  does not provide  any  assurance  that a
position taken in reliance on such opinion will not be challenged by the Service
and does not constitute any representation or warranty that such position, if so
challenged, will not be rejected by a court.

This  opinion  addresses  only the specific  United  States  federal  income tax
consequences of the Transaction set forth below,  and does not address any other
federal,  state, local, or foreign income,  estate,  gift,  transfer,  sales, or
other tax consequences  that may result from the Transaction or any other action
(including any action taken in connection with the Transaction).

On the  basis  of and  subject  to  the  foregoing  and  in  reliance  upon  the
representations,  facts and assumptions  described  above, we are of the opinion
that the  acquisition by Acquiring Fund of the assets of Acquired Fund solely in
exchange  for the  issuance of  Acquiring  Fund Shares to Acquired  Fund and the
assumption of the Acquired Fund  Liabilities by Acquiring Fund,  followed by the
distribution  by Acquired  Fund, in  liquidation  of Acquired Fund, of Acquiring
Fund Shares to Acquired Fund  shareholders  in exchange for their  Acquired Fund
Shares and the termination of Acquired Fund, will constitute a  "reorganization"
within the meaning of Section 368(a) of the Code.



John Hancock Biotechnology Fund
John Hancock Health Sciences Fund
__________________________, 2005
Page 3


This opinion is being delivered to you solely in connection with the closing
condition set forth in Section 8.6 of the Agreement. This opinion is intended
solely for the benefit of you and the shareholders of the Acquired Fund and it
may not be relied upon for any other purpose or by any other person or entity,
and may not be made available to any other person or entity, without our prior
written consent.



                                                Very truly yours,

                                                WILMER CUTLER PICKERING
                                                HALE AND DORR LLP


                                                By:      ______________________