Prospectus Supplement
                         (To Prospectus Dated May 2, 2000)

                                  $500,000,000

                5% Convertible Subordinated Notes due February 1, 2007

                            -------------------------

     This prospectus supplement relates to the resale by the holders of
Rational Software Corporation 5% Convertible Subordinated Notes Due February
1, 2000 and the shares of common stock, $.01 par value per share, issuable
upon the conversion of the notes.

     This prospectus supplement should be read in conjunction with, and may
not be delivered or utilized without, the prospectus dated May 2, 2000,
including any amendments or supplements thereto.  The terms of the notes
are set forth in the prospectus.

     The information in the table appearing under the heading "Selling
Securityholders" in the prospectus is amended by adding the information below
with respect to persons not previously listed in the prospectus or in any
amendments or supplements thereto, and by superceding the information with
respect to persons previously listed in the prospectus or in any amendments
or supplements thereto that are listed below:





                          Principal
                          Amount at
                         Maturity of                  Number of
                            Notes                     Shares of
                        Beneficially  Percentage of  Common Stock  Percentage of
                         Owned That       Notes       That May     Common Stock
          Name           May Be Sold   Outstanding     Be Sold     Outstanding
- -----------------------  -----------   -----------   -----------   -----------
                                                       

Allstate Insurance
Company                    2,125,000         0.43%       59,493         0.0%

Ariston Convertible
Securities Fund              700,000         0.14%       19,598         0.0%

Ariston Internet
Convertible Fund              25,000         0.01%          700         0.0%

Deutche Bank AG            5,167,000         1.03%      144,658         0.1%

Elf Aquitaine                300,000         0.06%        8,399         0.0%

First Union Securities
Inc.                       3,100,000         0.62%       86,789         0.0%

Goldman Sachs and
Company                      890,000         0.18%       24,917         0.0%

Key Asset Management
as agent for the Victory
Convertible Securities
Fund                       1,000,000         0.20%       27,997         0.0%

Morgan Stanley Dean
Witter Convertible
Securities Trust           1,750,000         0.35%       48,994         0.0%

Oxford, Lord Abbet
& Co.                      1,600,000         0.32%       44,795         0.0%


                            -------------------------

     The Date of This Prospectus Supplement Is September 9, 2000.