Ambac Financial (AMBC) 10-Q 2003 Q2 Quarterly report

EXHIBIT 32.1

Certification of CEO Pursuant to
18 U.S.C. Section 1350,
as Adopted Pursuant to
Section 906 of the Sarbanes-Oxley Act of 2002

In connection with the Quarterly Report on Form 10-Q of Ambac Financial Group, Inc. (the “Company”) for the quarter ending June 30, 2003 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), Phillip B. Lassiter, as Chief Executive Officer of the Company, hereby certifies, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that, to the best of my knowledge:

          (1)     The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

          (2)     The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ PHILLIP B. LASSITER
Name:	Phillip B. Lassiter
Title:	Chairman and Chief Executive Officer
Date:	August 14, 2003