Advisory Board 10-Q 2004 Q4 Quarterly report

Exhibit 32.1

THE ADVISORY BOARD COMPANY

CERTIFICATION PURSUANT TO
18 U.S.C. SECTION 1350,
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

     The undersigned hereby certifies, in his capacity as an officer of The Advisory Board Company (the “Company”), for purposes of 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

•   the Quarterly Report of the Company on Form 10-Q for the period ended December 31, 2004 fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934; and

•   the information contained in such report fairly presents, in all material respects, the financial condition and results of operation of the Company.

Dated: February 9, 2005

/s/ Frank J. Williams                              
Frank J. Williams, Chairman and
Chief Executive Officer

/s/ David L. Felsenthal                         
David L. Felsenthal, Chief Financial
Officer, Secretary and Treasurer