CERTIFICATIONS PURSUANT TO SECTION 906
EX-99.906CERT

                                  CERTIFICATION

R. Jay Gerken, Chief Executive Officer, and Richard Peteka, Chief Financial
Officer of the of Smith Barney Investment Series - Smith Barney Large Cap Core
Fund, each certify to the best of his or her knowledge that:

   1. The Registrant's periodic report on Form N-CSR for the period ended April
30, 2003 (the "Form N-CSR") fully complies with the requirements of section
15(d) of the Securities Exchange Act of 1934, as amended; and

   2. The information contained in the Form N-CSR fairly presents, in all
material respects, the financial condition and results of operations of the
Registrant.

Chief Executive Officer                        Chief Financial Officer
Smith Barney Investment Series -               Smith Barney Investment Series -
Smith Barney Large Cap Core Fund               Smith Barney Large Cap Core Fund


/s/ R. Jay Gerken                                    /s/ Richard Peteka
- ---------------------------                          ---------------------------
R. Jay Gerken                                        Richard Peteka
Date: June 27, 2003                                  Date: June 27, 2003

A signed original of this written statement required by Section 906, or other
document authenticating, acknowledging, or otherwise adopting the signature that
appears in typed form within the electronic version of this written statement
required by Section 906, has been provided to Smith Barney Investment Series
- - Smith Barney Large Cap Core Fund and will be retained by Smith Barney
Investment Series - Smith Barney Large Cap Core Fund and furnished to the
Securities and Exchange Commission or its staff upon request.

This certification is being furnished to the Commission solely pursuant to 18
U.S.C. (S) 1350 and is not being filed as part of the Form N-CSR with the
Commission.