SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    ---------

                                    FORM 8-A


                FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                     PURSUANT TO SECTION 12(b) OR (g) OF THE
                         SECURITIES EXCHANGE ACT OF 1934


                            INTEGRATED SYSTEMS, INC.
             ------------------------------------------------------
             (Exact name of registrant as specified in its charter)


             California                                   94-2658153
- ----------------------------------------              ------------------
(State of incorporation or organization)              (I.R.S. Employer
                                                      Identification no.)


          3260 Jay Street
      Santa Clara, California                              95054-3309
- ----------------------------------------                   ----------
(Address of principal executive offices)                   (Zip code)


If this Form relates to the                If this Form relates to the
registration of a class of securities      registration of a class of securities
pursuant to Section 12(b) of the           pursuant to Section 12(g) of the
Exchange Act and is effective              Exchange Act and is effective
pursuant to General Instruction            pursuant to General Instruction
A.(c), please check the following          A.(d), please check the following
box.  [  ]                                 box.  [x]


                     Securities to be registered pursuant to
                         Section 12(b) of the Act: None.


        Securities to be registered pursuant to Section 12(g) of the Act:


                         Preferred Stock Purchase Rights
- --------------------------------------------------------------------------------
                                (Title of Class)



Item 1:           Description of Registrant's Securities to be Registered:

                  On September  24, 1998,  the Board of Directors of  Integrated
Systems,  Inc.  (the  "Company")  declared a  dividend  of one  preferred  share
purchase right (a "Right") for each  outstanding  share of common stock,  no par
value  (the  "Common  Shares"),  of the  Company.  The  dividend  is  payable to
stockholders of record on October 15, 1998 (the "Record Date"). In addition, one
Right  shall be issued  with each  Common  Share that  becomes  outstanding  (i)
between  the  Record  Date  and  the  earliest  of the  Distribution  Date,  the
Redemption Date and the Final  Expiration Date (as such terms are defined in the
Agreement) or (ii) following the  Distribution  Date and prior to the Redemption
Date or Final  Expiration  Date,  pursuant to the  exercise of stock  options or
under any employee  plan or  arrangement  or upon the  exercise,  conversion  or
exchange of other  securities of the Company,  which options or securities  were
outstanding  prior to the Distribution  Date. Each Right entitles the registered
holder to purchase  from the Company  one  two-hundredth  of a share of Series A
Junior Participating  Preferred Stock, no par value (the "Preferred Shares"), of
the Company,  at a price of $55.00 per one  two-hundredth  of a Preferred  Share
(the "Purchase Price"), subject to adjustment.  The description and terms of the
Rights are set forth in a Rights Agreement (the "Rights  Agreement") between the
Company and  ChaseMellon  Shareholder  Services,  as Rights  Agent (the  "Rights
Agent").

         Until  the  earlier  to  occur  of  (i)  10  days  following  a  public
announcement  or  disclosure  that a person or group of affiliated or associated
persons (an "Acquiring  Person"),  has acquired  beneficial  ownership of 20% or
more of the  outstanding  Common  Shares or (ii) 10 business days (or such later
date as may be determined by action of the Board of Directors  prior to the time
a person or group becomes an Acquiring Person), following the announcement of an
intention to make a tender  offer or exchange  offer the  consummation  of which
would result in a person or group  becoming an Acquiring  Person (the earlier of
such dates being called the "Distribution  Date"), the Rights will be evidenced,
with  respect  to any of the Common  Share  certificates  outstanding  as of the
Record Date,  by such Common Share  certificates  with a copy of this Summary of
Rights attached thereto.  No person or group shall become an Acquiring Person if
the Board of Directors of the Company  determines in good faith that a person or
group who would otherwise be an Acquiring Person has become such  inadvertently,
and such person or group as promptly as practicable takes such actions as may be
necessary  so that  such  person  or group  would no  longer  be  considered  an
Acquiring Person.

                  The Rights  Agreement  provides that,  until the  Distribution
Date, the Rights will be transferred with and only with the Common Shares. Until
the Distribution Date (or earlier  redemption or expiration of the Rights),  new
Common Share  certificates  issued after the Record Date,  upon  transfer or new
issuance of Common  Shares,  will  contain a notation  incorporating  the Rights
Agreement by reference.  Until the Distribution  Date (or earlier  redemption or
expiration of the Rights),  the surrender for transfer of any  certificates  for
Common Shares outstanding as of the Record Date, even without such notation or a
copy of the Summary of Rights being attached  thereto,  will also constitute the
transfer of the Rights  associated  with the Common Shares  represented  by such
certificate.  As soon as practicable  following the Distribution Date,  separate
certificates  evidencing  the Rights  ("Right  Certificates")  will be mailed to
holders  of record of the  



Common  Shares as of the Close of  Business  on the  Distribution  Date and such
separate Right Certificates alone will evidence the Rights.

                  The Rights are not exercisable  until the  Distribution  Date.
The Rights will expire on  September  30,  2008 (the "Final  Expiration  Date"),
unless the Final  Expiration  Date is  extended or unless the Rights are earlier
redeemed or exchanged by the Company, in each case, as described below.

                  The Purchase Price payable, and the number of Preferred Shares
or other  securities  or  property  issuable,  upon  exercise  of the Rights are
subject to adjustment from time to time to prevent  dilution (i) in the event of
a stock dividend on, or a subdivision,  combination or reclassification  of, the
Preferred  Shares,  (ii) upon the grant to  holders of the  Preferred  Shares of
certain  rights or warrants to subscribe for or purchase  Preferred  Shares at a
price, or securities  convertible into Preferred Shares with a conversion price,
less than the then current  market price of the  Preferred  Shares or (iii) upon
the distribution to holders of the Preferred Shares of evidences of indebtedness
or assets  (excluding  regular  periodic cash  dividends paid out of earnings or
retained  earnings or dividends  payable in Preferred Shares) or of subscription
rights or warrants (other than those referred to above).

                  The  number  of  outstanding  Rights  and  the  number  of one
two-hundredth of a Preferred Share issuable upon exercise of each Right are also
subject to  adjustment  in the event of a stock  dividend  on the Common  Shares
payable in Common Shares or subdivisions,  consolidations or combinations of the
Common Shares occurring, in any such case, prior to the Distribution Date.

                  Preferred Shares  purchasable upon exercise of the Rights will
not be redeemable. Each Preferred Share will be entitled to a quarterly dividend
payment of 200 times the  dividend  declared per Common  Share.  In the event of
liquidation,  each Preferred Share will be entitled to a $2.00  preference,  and
thereafter the holders of the Preferred  Shares will be entitled to an aggregate
payment of 200 times the aggregate payment made per Common Share. Each Preferred
Share will have 200 votes,  voting together with the Common Shares.  Finally, in
the event of any merger,  consolidation  or other  transaction  in which  Common
Shares are exchanged, each Preferred Share will be entitled to receive 200 times
the amount  received per Common  Share.  These rights are protected by customary
antidilution provisions.

                  Because  of the  nature  of the  Preferred  Shares'  dividend,
liquidation and voting rights, the value of the one two-hundredth  interest in a
Preferred Share  purchasable upon exercise of each Right should  approximate the
value of one Common Share.

                  In the event that any  person  becomes  an  Acquiring  Person,
unless the event causing the Designated  Percentage  threshold to be crossed and
the  Person to thereby  become an  Acquiring  Person is a merger or  acquisition
described  in the next  paragraph,  each  holder of a Right,  other than  Rights
beneficially owned by the Acquiring Person (which will thereafter be void), will
thereafter  have the right to receive upon exercise that number of Common Shares
having a market value of two times the exercise  price of the Right on the terms
and conditions set forth in the Rights  Agreement.  If the Company does not have
authorized but unissued  Common Shares  sufficient to satisfy such obligation to
issue  Common  Shares,  the Company is  obligated to


                                       2


deliver upon payment of the exercise price of a Right an amount of cash or other
securities  equivalent in value to the Common Shares issuable upon exercise of a
Right.

                  In the event  that any person or group  becomes  an  Acquiring
Person  and the  Company  merges  into or  engages  in  certain  other  business
combination  transactions  with  an  Acquiring  Person  or  50% or  more  of its
consolidated  assets or  earning  power are sold to an  Acquiring  Person,  each
holder of a Right, other than Rights  beneficially owned by an Acquiring Person,
will thereafter have the right to receive, upon the exercise thereof at the then
current  exercise  price of the Right,  that number of shares of common stock of
the acquiring  company which at the time of such  transaction will have a market
value of two times the exercise price of the Right.

                  At any time after any person  becomes an Acquiring  Person and
prior  to the  acquisition  by  such  person  or  group  of 50% or  more  of the
outstanding  Common  Shares,  the Board of Directors of the Company may exchange
the Rights  (other than  Rights  owned by such person or group which have become
void),  in whole or in part, at an exchange  ratio of one Common  Share,  or one
two-hundredth  of a  Preferred  Share (or of a share of a class or series of the
Company's preferred stock having equivalent rights, preferences and privileges),
per Right (subject to adjustment).

                  With certain  exceptions,  no adjustment in the Purchase Price
will be required until cumulative  adjustments require an adjustment of at least
1% in such Purchase Price. No fractional  Preferred Shares will be issued (other
than fractions which are integral  multiples of one two-hundredth of a Preferred
Share,  which may, at the  election of the Company,  be evidenced by  depository
receipts) and in lieu  thereof,  an adjustment in cash will be made based on the
market price of the  Preferred  Shares on the last trading day prior to the date
of exercise.

                  At any time prior to such time as a person or group becomes an
Acquiring Person, the Board of Directors of the Company may redeem the Rights in
whole, but not in part, at a price of $0.001 per Right (the "Redemption Price").
The  redemption of the Rights may be made  effective at such time, on such basis
and with such  conditions as the Board of Directors in its sole  discretion  may
establish.  After the period for redemption of the Rights has expired, the Board
may not amend the Rights  Agreement to extend the period for  redemption  of the
Rights. Immediately upon any redemption of the Rights, the right to exercise the
Rights  will  terminate  and the only right of the  holders of Rights will be to
receive the Redemption Price.

                  The terms of the Rights may be amended by a resolution  of the
Board of Directors without the consent of the holders of the Rights, except that
from and after such time as a person or group  becomes an Acquiring  Person,  no
such  amendment may adversely  affect the interests of the holders of the Rights
(other than an Acquiring Person).

                  Until a Right is exercised,  the holder thereof, as such, will
have no rights as a stockholder of the Company,  including,  without limitation,
the right to vote or to receive dividends.

                  As of  September  23,  1998,  there  were  approximately  23.3
million  of  the  Company's  Common  Shares   outstanding.   Each  Common  Share
outstanding at the close of


                                       3


business on October 15, 1998 will  receive one Right.  As long as the Rights are
attached  to the  Common  Shares,  one  additional  Right  shall be deemed to be
delivered  for each Common  Share  issued or  transferred  by the Company in the
future,  including  but not limited to Common  Shares  issuable upon exercise of
options  granted by the Company.  Five  hundred  thousand  Preferred  Shares are
initially  reserved for issuance upon exercise of the Rights,  such number to be
subject to adjustment from time to time in accordance with the Rights Agreement.

                  The Rights Agreement,  which specifies the terms of the Rights
and which includes as exhibits  thereto the form of Certificate of Determination
of Preferences of Series A Junior  Participating  Preferred  Stock,  the Form of
Right  Certificate  and the form of  Summary  of  Rights to  Purchase  Preferred
Shares,  is  filed  as  Exhibit  4.1  hereto.  A  copy  of  the  Certificate  of
Determination of Preferences of Series A Junior Participating Preferred Stock as
filed with the California  Secretary of State,  which specifies the terms of the
Preferred Shares, is filed as Exhibit 3.2 hereto.  The  aforementioned  exhibits
hereto are incorporated  herein by reference,  and the foregoing  description of
the Rights and  Preferred  Shares is  qualified  in its entirety by reference to
such exhibits.


                                       4


Item 2:           Exhibits
                  --------

                  3.1      Articles of Incorporation  of Registrant,  as amended
                           to  date.   (Incorporated  by  reference  to  Exhibit
                           3.01(i) to  Registrant's  Annual  Report on Form 10-K
                           for the year ended February 28, 1996).

                  3.2      Certificate   of    Determination    of   Preferences
                           specifying   the   terms  of  the   Series  A  Junior
                           Participating Preferred Stock of Registrant, as filed
                           with  the   Secretary   of  State  of  the  State  of
                           California on October 1, 1998.

                  4.1      Rights  Agreement  dated  September  30, 1998 between
                           Registrant and ChaseMellon  Shareholder  Services, as
                           Rights Agent, which includes as Exhibit A the form of
                           Certificate of Determination of Preferences of Series
                           A Junior Participating  Preferred Stock, as Exhibit B
                           the Form of Right  Certificate  and as  Exhibit C the
                           Summary of Rights to Purchase  Preferred Shares.  The
                           Right  Certificates  will  not be  distributed  until
                           after the Distribution  Date (as such term is defined
                           in the Rights Agreement).


                                       5


                                    SIGNATURE



                  Pursuant to the  requirements  of Section 12 of the Securities
Exchange Act of 1934, the Registrant has duly caused this registration statement
to be signed on its behalf by the undersigned, thereto duly authorized.

Dated: October 6, 1998

                                        INTEGRATED SYSTEMS, INC.



                                        By:    /s/ Joseph Addiego
                                               ---------------------------------
                                               Joseph Addiego
                                               Chief Executive Officer



                                       6


                                  EXHIBIT INDEX




Exhibit
- -------

3.1      Articles  of   Incorporation   of  Registrant,   as  amended  to  date.
         (Incorporated  by reference to Exhibit 3.01(i) to  Registrant's  Annual
         Report on Form 10-K for the year ended February 28, 1996).

3.2      Certificate of Determination of Preferences specifying the terms of the
         Series A Junior Participating  Preferred Stock of Registrant,  as filed
         with the  Secretary of  State of the State of  California on October 1,
         1998.

4.1      Rights  Agreement  dated  September  30, 1998  between  Registrant  and
         ChaseMellon  Shareholder  Services,  as Rights Agent, which includes as
         Exhibit A the form of  Certificate of  Determination  of Preferences of
         Series A Junior Participating Preferred Stock, as Exhibit B the Form of
         Right  Certificate  and as Exhibit C the  Summary of Rights to Purchase
         Preferred Shares.  The Right Certificates will not be distributed until
         after the  Distribution  Date (as such term is  defined  in the  Rights
         Agreement).