[AHP Logo]                    [Immunex Logo]








FOR IMMEDIATE RELEASE

American Home Products Corporation                   Immunex Corporation
Media Contact:                                       Media Contact:
Lowell Weiner                                        Tim Warner
(973) 660-5013                                       (206) 470-4193

Investor Contact:                                    Investor Contact:
Thomas Cavanagh                                      Mark Leahy
(973) 660-5706                                       (206) 389-4363

                          AHP AND IMMUNEX TAKE ACTIONS

                     TO SUPPORT CONTINUED GROWTH OF IMMUNEX

     Madison,  N.J. and Seattle,  WA,  August 9, 2000 - American  Home  Products
Corporation  (NYSE:AHP) and Immunex Corporation  (NASDAQ:IMNX) today announced a
number of actions that have been taken by the two companies.  These actions will
support  Immunex in executing its long-term  growth strategy and are intended to
enable AHP to  monetize a portion of its  highly  successful  investment  in the
biotech  company  while  continuing  to be a  major  participant  in the  future
development and growth of Immunex.

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     Immunex  today has filed a shelf  registration  statement  that would allow
Immunex to sell up to 20 million shares of newly-issued  Immunex common stock in
a primary  offering  and AHP to sell up to 50 million  shares of Immunex  common
stock in a secondary offering, market conditions permitting.

     The  combined  effect of the  equity  offering,  if and when  executed,  is
expected to reduce AHP's  ownership stake in Immunex from  approximately  55% to
approximately  43%. If AHP's  ownership  falls below 45%, AHP will retain two of
its three  seats on the Immunex  board and AHP and  Immunex  have agreed in such
event to increase the number of independent directors from three to four.

     Key  elements  of the new  business  arrangements  between  AHP and Immunex
include the future  sale by AHP to Immunex of AHP's  recently  acquired  biotech
manufacturing  facility in Rhode Island,  which as previously disclosed is being
retrofitted to increase  manufacturing  capacity of ENBREL(R)  (etanercept).  In
addition,  AHP has agreed to provide Immunex with financing  guarantees to third
party  lenders of up to $550 million  toward the cost of Immunex's  proposed new
research and technology  center in Seattle.  Finally,  AHP agreed to convert its
existing $450 million convertible subordinated Immunex note into Immunex

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common  stock  concurrently  with the  financing  guarantees.  All existing
licensing  and  marketing  rights to ENBREL  between  the two  companies  remain
unchanged.   "We  are  pleased  to  have  reached  such  a  mutually  beneficial
arrangement  with  Immunex,"  said John R.  Stafford,  AHP's  Chairman and Chief
Executive  Officer.  "Immunex  will be able to continue its growth  strategy and
increase  its  research  and  manufacturing  capabilities,  while AHP is able to
realize a portion of our  investment.  We will continue to have a very important
business  relationship  with  Immunex and will remain its largest  shareholder,"
added Mr.  Stafford.  "Our new  arrangement  with AHP increases our  operational
flexibility and positions  Immunex very well financially for continued  growth,"
said Ed Fritzky,  Immunex  chairman  and CEO.  "This marks an  evolution  in our
relationship with AHP from one of a majority-owned entity to business partner."

     American  Home  Products   Corporation  is  one  of  the  world's   largest
research-based pharmaceutical and health care products companies. It is a leader
in the discovery, development, manufacturing and marketing of prescription drugs
and over-the-counter medications. It is also a leader in vaccines, biotechnology
and animal health care.

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     Immunex Corporation is a  biopharmaceutical  company dedicated to improving
lives through  immune system science  innovations.  The statements in this press
release  that are not  historical  facts  are  forward-looking  statements  that
involve risks and uncertainties including,  without limitation, risks associated
with the inherent uncertainty of pharmaceutical  research,  product development,
product regulatory approval and compliance, product commercialization,  reliance
on third party manufacturers,  the impact of competitive products, patent issues
and other risks or uncertainties,  including those detailed from time to time in
AHP's and Immunex's periodic reports,  including  quarterly reports on Form 10-Q
and the annual  report on Form  10-K,  filed with the  Securities  and  Exchange
Commission. Actual results may differ from forward-looking statements.

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