Exhibit 10.8

                         PHARMACEUTICAL RESOURCES, INC.
                                  One Ram Ridge
                          Spring Valley, New York 10977


                                                            CONFIDENTIAL

                                                            March 25, 1998


Clal Pharmaceutical Industries Ltd.                   Merck KGaA
Clal House                                            Frankfurter Strasse 250
5, Druyanov Street                                    64271 Darmstadt Germany
Tel Aviv 63143
ISRAEL


Gentlemen:

     This  letter  agreement  sets  forth our  agreement  regarding  a  possible
transaction involving the purchase of shares of common stock, par value $.01 per
share (the "Common Stock"),  of Pharmaceutical  Resources,  Inc. (the "Company")
owned  by Clal  Pharmaceutical  Industries  Ltd.  ("Clal").  The  Company  is in
confidential  negotiations  regarding  a possible  investment  in the Company by
Merck  KGaA  or one of its  affiliates  (collectively,  "Merck").  No  agreement
between the Company and Merck has been reached. with respect to such transaction
(the "Merck Transaction").

     In connection  with the possible  investment  in the Company by Merck,  the
Company, Merck and Clal agree as follows:

1.  Concurrently  with,  and  subject  to, the closing  (the  "Closing")  of the
transactions  contemplated by a definitive  stock purchase  agreement  presently
being  discussed to be entered  into between the Company and Merck  regarding an
investment by Merck in the Company (the "Purchase Agreement"):

     (a) Clal shall sell to Merck, and Merck shall purchase from Clal, 1,313,272
     shares of Common  Stock (the  "Tranche A Shares").  The per share  purchase
     price for the  Tranche A Shares,  which  shall be payable  at the  Closing,
     shall be the greater of (i) $2.00 and (ii) the per share  purchase price to
     be paid by  Merck to the  Company  for the  shares  of  Common  Stock to be
     acquired  by Merck at the  Closing  (such  greater  price  being the "Merck
     Purchase Price").




     (b) Clal shall sell to Merck,  and Merck shall  purchase  from Clal, at the
     Closing,  500,000  additional  shares  of  Common  Stock  (the  "Tranche  B
     Shares").  The per share  purchase  price for the  Tranche B Shares,  which
     shall be payable at the Closing,  shall be the Merck Purchase Price. On the
     second  anniversary  of the  Closing,  Merck shall pay to Clal an amount in
     respect of each  Tranche B Share  equal to the  excess,  if any, of (i) the
     weighted  average  price of all trades in the shares of Common Stock on The
     New York Stock  Exchange  ("Fair  Market  Value")  during  the thirty  (30)
     trading days  immediately  preceding the second  anniversary of the date of
     the Closing over (ii) the Merck Purchase Price.

     (c) All payments to Clal  pursuant to Paragraphs 1 and 2 hereof shall be by
     wire transfer of  immediately  available  funds or by certified or official
     bank check.

     (d) Merck hereby acknowledges that (i) all shares of Common Stock purchased
     by Merck from Clal will be purchased for investment purposes only without a
     view to the  resale  or  distribution  thereof  and may  not be  resold  or
     transferred  other than in compliance  with all applicable  securities laws
     and (ii) in connection  with such  purchase,  Clal is, subject to Paragraph
     2(a)  hereof,  making  no  representations  or  warranties  of  any  nature
     whatsoever  other than that Clal is conveying to Merck good and  marketable
     title to such shares which shall be duly authorized,  validly issued, fully
     paid and  nonassessable,  free  and  clear of any  liens,  claims  or other
     encumbrances,   and  that  such  conveyance  will  not  conflict  with  any
     agreement, law or obligation applicable to Clal.

2.   (a)  Subject to  Paragraph  7 below,  during the period  commencing  on the
     Closing and ending three years and five U.S.  business days thereafter (the
     "Post-Closing  Period"),  Clal shall not,  directly  or  indirectly,  sell,
     assign,  pledge,  transfer,  create or purchase any option or warrant on or
     with respect to, enter into any transaction  shifting a substantial portion
     of the  benefits  and  burdens of  ownership  of, or  otherwise  dispose of
     (collectively,  "Transfer"), or enter into a contract or agreement (whether
     or not contingent) to Transfer, any of the remaining shares of Common Stock
     beneficially  owned  by  Clal  (the  "Tranche  C  Shares").   Clal  further
     represents and warrants that immediately  following the Closing,  Clal will
     beneficially  own 500,000  shares of Common Stock,  all of which shares are

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     subject to the put and call  options  described in  Paragraphs  2(b)(i) and
     (ii) below. These 500,000 shares of Common Stock will represent Clal's then
     entire  remaining  equity  interest in the Company,  including  the 186,000
     shares of Common Stock delivered to Clal pursuant to the Third Amendment to
     the Stock  Purchase  Agreement,  dated July 28, 1997,  between the Company,
     Clal  and  PRI-Research,  Inc.,  and  Clal  represents  that  it  holds  no
     unexercised  options,  warrants or other  rights with respect to any Common
     Stock as of the date hereof.

     (b)(i) During the five U.S.  business day period commencing on the last day
     of the  Post-Closing  Period,  Clal shall have the right to cause Merck (or
     the Company,  if Merck and the Company  shall  agree) to purchase,  and, if
     Clal so elects,  Merck  and/or the Company  shall  purchase,  the Tranche C
     Shares at a price of $2.50 per share.

     (ii) In the event that Clal shall not have  exercised the right provided in
     Paragraph  2(b)(i)  hereof,  Clal,  Merck and/or the Company shall have the
     right to exercise the option provided in this Paragraph  2(b)(ii),  in each
     case by  providing  written  notice of such  exercise  to each of the other
     parties  hereto within five U.S.  business days following the expiration of
     the five U.S.  business day period  referred to in Paragraph 2(b) (i). Upon
     the exercise of such option:

     (A) Clal shall  seek to sell any or all of the  Tranche C Shares on The New
     York Stock  Exchange for a period of ninety  trading days  beginning on the
     third trading day following exercise of the option; provided, however, that
     Clal shall not effect any such sale without the prior  consent of Merck and
     the Company,  and Clal shall use its best efforts to effect each sale which
     Merck and the Company shall direct Clal to effect; and

     (B) within five U.S.  business  days  following  the  expiration  of the 90
     trading  day period  referred  to above,  Merck  and/or the  Company  shall
     purchase from Clal all of the Tranche C Shares not sold by Clal during such
     90 trading  day period (if any),  and shall pay to Clal an amount  equal to
     the amount,  if any, by which (I) the product of 500,000  multiplied by the
     Fair Market Value during the 30 trading days immediately preceding the last
     day of the Post-Closing Period exceeds (II) the aggregate proceeds realized
     by Clal from  sales of Tranche C Shares  during  the 90 trading  day period
     referred to herein.

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3. All shares of Common Stock sold by Clal pursuant to this  agreement  shall be
duly authorized,  validly issued, fully paid and nonassessable and shall be free
and clear  from all  liens,  pledges,  claims  and other  agreements,  including
warrants, options and voting agreements.

4. Except as otherwise  contemplated  in Paragraph 1 hereof,  and in addition to
the  restrictions  set forth in  Paragraph  2(a)  hereof,  from the date  hereof
through  the  occurrence  of the first to occur of (i) the  termination  of this
agreement  in  accordance  with  Paragraph  7  hereof  and  (ii)  the end of the
Post-Closing Period, neither Clal nor any person under Clal's control, shall (w)
purchase or otherwise  acquire any additional  shares of Common Stock,  options,
warrants or other  securities of the Company,  (x) Transfer any shares of Common
Stock beneficially  owned,  directly or indirectly,  by Clal, (y) enter into any
agreement  or  arrangement  with any person or entity  (other than the  Company)
concerning the voting,  holding or transferring of any shares of the Company, or
initiate, propose or participate in any transaction involving the Company or (z)
recommend any person to engage in the activities in (w), (x) or (y) above.

5. Effective upon the Closing:  (i) the Stock  Purchase  Agreement,  between the
Company and Clal, dated March 25, 1995, as amended (the "Clal Agreement"), shall
be terminated in its entirety with no further obligations, liabilities or rights
on the  part  of the  parties  thereunder,  and  (ii)  the  Registration  Rights
Agreement,  between the Company  and Clal,  dated May 1, 1995,  shall be amended
hereby and shall  provide that Clal shall not be entitled to exercise any of its
rights  thereunder  during  the  Post-Closing  Period.  Clal  hereby  agrees to,
notwithstanding any other agreement that it may have with the Company or others,
vote all shares of Common Stock which it owns (beneficially and/or of record) in
favor of the Merck  Transaction (and all related matters) if such Transaction is
approved  by the  Company's  Board of  Directors.  In the event of any  conflict
between the terms of this  agreement and the Clal  Agreement,  the terms of this
agreement shall govern.
 
6. The execution  and delivery of this  agreement  and the  consummation  of the
transactions   contemplated  hereby  shall  in  no  way  affect  or  modify  the
obligations of (i) P.R.I. Research, Inc. ("PRI Research") under the Non-Recourse
Promissory  Note,  dated July 28, 1997,  (ii) the Company,  PRI Research,  Clal,
C.T.P.  Research and  Development  (1995) Ltd.,  Clal  Pharmaceutical  Resources
(1995) Ltd. or Clal  Pharmaceutical  Resources L.P. under the letter  agreement,
dated July 28,  1997,  with respect to the purchase of interests by PRI Research
in the joint venture of the Company and Clal and any and all documents  executed
in connection therewith, or (iii) the transactions contemplated thereby.


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7. Each of Clal,  the Company and Merck shall have the right to  terminate  this
agreement  without  further  obligation to any of the parties hereto (except for
Paragraphs 8, 9, 10 and 11 below) by written  notice to the other parties hereto
(i) after March 27, 1998, unless a definitive Purchase Agreement with respect to
the Merck Transaction has theretofore been executed by each party thereto,  (ii)
after July 15, 1998, unless the Closing has theretofore occurred and (iii) after
April 3, 1998,  unless the board of directors of Merck has theretofore  approved
the Purchase Agreement.

8. The Company,  Merck and Clal agree to keep strictly confidential the contents
of this agreement,  the fact that discussions between the Company and Merck have
occurred,  the terms of such discussions and all of the other matters  discussed
herein,  until after such time as the Company has  disclosed  such matters under
applicable  securities  laws or the  rules of the stock  exchanges  on which the
Common Stock is traded; provided,  however, that, notwithstanding the foregoing,
Clal may  disclose  such matters at such time,  and to such extent,  as required
under applicable securities laws.

9. All notices hereunder shall be in writing and shall be given:

         (a)      if to the Company,
 
                  One Ram Ridge Road
                  Spring Valley, New York 10977
                  Attention: Kenneth I.  Sawyer, President
                  Fax number: (914) 425-7922

                  with a copy to,

                  Hertzog, Calamari & Gleason
                  100 Park Avenue
                  New York, New York 10017
                  Attention: Stephen Ollendorff, Esq.
                           and Stephen R.  Connoni, Esq.
                  Fax number: (212) 213-1199

         (b)      if to Merck,
 
                  Frankfurter Strasse 250
                  64271 Darmstadt Germany
                  Attention: Dr.  Rudi Neirinckx
                  Fax number: (011 49) 6151 72 3435

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                  with a copy to,

                  Coudert Brothers
                  1114 Avenue of the Americas
                  New York, New York 10036-7703
                  Attention: Edwin S.  Matthews, Jr.
                  Fax number: (212) 626-4120

         (c)      if to Clal,
 
                  Clal Pharmaceutical Industries Ltd.
                  Clal House
                  5 Druyanov Street
                  Tel Aviv 63143 Israel
                  Attention: Ken Lalo, General Counsel
                  Fax number:  011 972 3629 3633

                  With a copy to,

                  Weil, Gotshal & Manges LLP
                  767 Fifth Avenue
                  New York, New York 10153
                  Attention:  David P. Stone, Esq.
                  Fax number:  (212) 310 - 8007
 
Any notice shall be deemed to have been given,  if personally  delivered or sent
by express  commercial  courier or  delivery  service or by  telegram,  telefax,
telefax or facsimile transmission. Any notice given in any other manner shall be
deemed given when actually received.

10. This agreement shall be governed in accordance with the laws of the State of
New York, without regard to its conflicts of laws principles. For the purpose of
this letter agreement,  "U.S.  Business Day" shall mean any day except Saturday,
Sunday  and any  other  day on  which  commercial  banks  in New  York  City are
authorized by law to close.

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11.  This  agreement  shall not be amended or  (subject  to  Paragraph  7 above)
terminated,  and no provision hereof may be waived, except pursuant to a written
instrument executed by each of the parties hereto.


                                                  Sincerely,

                                                  PHARMACEUTICAL RESOURCES, INC.


                                                   By: /s/ Kenneth I. Sawyer 
                                                      __________________________
                                                      Name:  Kenneth I. Sawyer

                                                      Title: President


ACCEPTED AND AGREED TO:

CLAL PHARMACEUTICAL INDUSTRIES LTD.


By: /s/ Ken Lalo
   --------------------------------
   Name:  Ken Lalo
   Title: General Counsel

DATED:  March 25, 1998


ACCEPTED AND AGREED TO:

MERCK KGaA



By: /s/ Rudi D. Neirinckx          
   --------------------------------
   Name:  Rudi D. Neirinckx
   Title: Head New Business, Merck KGaA

DATED: March 25, 1998
 
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