Exhibit 99.1

NOT FOR IMMEDIATE RELEASE
Contact: Integrated Systems, Inc.
Investor Relations, 408/542-1570
ir@isi.com




                Integrated Systems Adopts Shareholder Rights Plan

         SUNNYVALE, Calif.--(BUSINESS WIRE)--Sept. 30, 1998--Integrated Systems,
Inc.  (NASDAQ:INTS),  today  announced that its Board of Directors has adopted a
shareholder  rights plan designed to protect the long-term  value of the Company
for its shareholders during any future unsolicited acquisition attempt.

         The  plan  is  designed  to  give  the  Company's  Board  of  Directors
sufficient  time to study and respond to an  unsolicited  tender  offer or other
attempted  acquisition.  Adoption  of the plan was not made in  response  to any
specific  attempt to acquire the  Company or its shares,  and the Company is not
aware of any current efforts to do so.

         In  connection  with the plan,  the Board  declared a  dividend  of one
preferred  share  purchase  right for each share of the  Company's  common stock
outstanding  on October 15, 1998 (the  "Record  Date") and further  directed the
issuance of one such right with  respect to each share of the  Company's  common
stock that is issued after the Record Date, except in certain circumstances. The
rights will expire on September 30, 2008.

         The rights are  initially  attached to the  Company's  common stock and
will not trade separately. If a person or a group acquires 20 percent or more of
the Company's common stock (an "Acquiring Person"), or announces an intention to
make a tender offer for the  Company's  common stock the  consummation  of which
would result in a person or group becoming an Acquiring Person,  then the rights
will  be  distributed  (the  "Distribution  Date")  and  will  thereafter  trade
separately from the common stock.

         After the Distribution Date, each right may be exercised for 1/200th of
a share of a newly designated Series A Junior  Participating  Preferred Stock at
an exercise price of $55.00. The preferred stock has been structured so that the
value of 1/200th of a share of such preferred  stock will  approximate the value
of one share of common stock.

         Upon a person  becoming  an  Acquiring  Person,  holders  of the rights
(other than the Acquiring  Person) will have the right to acquire  shares of the
Company's common stock at a substantially discounted price.

         Additionally,  if a person becomes an Acquiring  Person and the Company
is acquired in a merger or other business combination,  or 50 percent or more of
its assets are



sold in a  transaction  with an Acquiring  Person,  the holders of rights (other
than the Acquiring Person) will have the right to receive shares of common stock
of the acquiring corporation at a substantially discounted price.

         After a person has become an Acquiring  Person,  the Company's Board of
Directors may, at its option,  require the exchange of outstanding rights (other
than those held by the Acquiring  Person) for common stock at an exchange  ratio
of one share of the company's common stock per right.

         The Board may redeem  outstanding  rights at any time prior to a person
becoming an Acquiring Person at a price of $0.001 per right. Prior to such time,
the terms of the rights may be amended by the Board.

         Integrated  Systems,  Inc. is a leading worldwide  provider of embedded
operating   software   and   simulation   and  control   design  tools  for  the
telecommunications/data  communications,  automotive, multimedia, entertainment,
office/retail   automation,   Internet,   aerospace  and  industrial  automation
industries.  Its software helps manufacturers  bring higher quality,  more fully
featured products to market faster. The Company's business model is based on the
sale of software  development  licenses for  creating  new products  followed by
runtime licenses for products using its embedded operating  software.  Sales and
services  offices  are  located  worldwide  in Asia,  Europe and North  America.
Additional   information   about  the  Company  is  available  at  its  Website:
http://www.isi.com.