N-CSR Item 11(b) - Exhibits: Certifications

                            SECTION 906 CERTIFICATION

Pursuant to 18 U.S.C.ss.  1350, the  undersigned  officers of Cash Trust Series,
Inc. on behalf of:  Government  Cash Series,  Municipal Cash Series,  Prime Cash
Series, Treasury Cash Series (the "Registrant"),  hereby certify, to the best of
our knowledge,  that the Registrant's  Report on Form N-CSR for the period ended
May 31, 2004 (the  "Report")  fully  complies with the  requirements  of Section
13(a) or 15(d),  as  applicable,  of the Securities and Exchange Act of 1934 and
that the information  contained in the Report fairly  presents,  in all material
respects, the financial condition and results of operations of the Registrant.


Dated:  July 22, 2004

/s/ J. Christopher Donahue
Title: President, Principal Executive Officer



Dated:  July 22, 2004

/s/ Richard J. Thomas
Title: Treasurer, Principal Financial Officer

This  certification is being furnished solely pursuant to 18 U.S.C.ss.  1350 and
is not being filed as part of the Report or as a separate disclosure document.