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                                                                EXHIBIT 4.3
                         AMENDMENT TO RIGHTS AGREEMENT


         AMENDMENT, dated as of April 21, 1997 (the "Amendment"), to the Rights
Agreement dated as of May 8, 1995 (the "Rights Agreement") between BMC
SOFTWARE, INC., a Delaware corporation (the "Company"), and BANKBOSTON NA 
(the "Rights Agent").

         WHEREAS, pursuant to and in compliance with Section 29 of the Rights
Agreement, the Company and the Rights Agent desire to amend the Rights
Agreement as set forth in this Amendment to reflect the foregoing;

         NOW, THEREFORE, in consideration of the premises and the mutual
agreements set forth herein and in the Rights Agreement, the parties hereto
hereby agree as follows:

                 1.       Section 8(b) of the Rights Agreement is hereby
         amended to read in its entirety as follows:

                 "The Purchase Price for each one one-thousandth (1/1000) of a
                 Preferred Share pursuant to the exercise of a Right shall be
                 increased to two hundred and fifty dollars ($250), shall be
                 subject to adjustment from time to time as provided in
                 Sections 12 and 14 hereof and shall be payable in lawful money
                 of the United States of America in accordance with paragraph
                 (c) below."

                 2.       Section 3(d) of the Rights Agreement is hereby
         amended by inserting after "May 8, 1995" in line 3 of the legend set
         forth therein the phrase "as amended as of April 21, 1997."

                 3.       The Form of Right Certificate attached to the Rights
         Agreement as Exhibit B is hereby amended by inserting after "May 8,
         1995" in line 3 thereof the phrase "as amended as of April 21, 1997."

                 4.       This Amendment shall be governed by and construed in
         accordance with the laws of the State of Delaware without regard to
         principles of conflicts of laws.

                 5.       This Amendment may be executed in any number of
         counterparts and each of such counterparts shall for all purposes be
         deemed to be an original, and all such counterparts shall together
         constitute but one and the same instrument.

                 6.       Except as expressly set forth herein, this Amendment
         shall not by implication or otherwise alter, modify, amend or in any
         way affect any of the terms, conditions, obligations, covenants or
         agreements contained in the Rights Agreement, all of which are
         ratified and affirmed in all respects and shall continue in full force
         and effect.
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                 IN WITNESS WHEREOF, the parties hereto have caused this
         Amendment to be duly executed and delivered and to become effective,
         all as of the day and year first above written.



ATTEST:                                                        BMC SOFTWARE, INC.
                                                        
By:                                                            By:                                                
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     Name:                                                     Name:                                                  
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     Title:                                                    Title:                                                 
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ATTEST:                                                        BANKBOSTON NA
                                                        
By:                                                            By:                                                
     -------------------------------------------------------         --------------------------------------------------
     Name:                                                     Name:                                                  
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     Title:                                                    Title:                                                 
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                               BMC SOFTWARE, INC.
                         AMENDMENT TO RIGHTS AGREEMENT
                                        
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