**Exhibit 31.1****Certification**I, Thomas L. Monahan III, certify that: 1. I have reviewed this quarterly report on Form 10-Q of The Corporate Executive Board Company;  2. Based on my knowledge, this report does not contain any untrue statement of a material factor omit to state a material fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleading with respect to theperiod covered by this report;  3. Based on my knowledge, the financial statements, and other financial information includedin this report, fairly present in all material respects the financial condition, results ofoperations and cash flows of the registrant as of, and for, the periods presented in thisreport;  4. The registrant’s other certifying officer and I are responsible for establishing andmaintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e)and 15d-15(e)) and internal control over financial reporting (as defined in Exchange ActRules 13a-15(f) and 15(d)-15(f)) for the registrant and have:  (a) Designed such disclosure controls and procedures, orcaused such disclosure controls and procedures to bedesigned under our supervision, to ensure that materialinformation relating to the registrant, including itsconsolidated subsidiaries, is made known to us byothers within those entities, particularly during theperiod in which this report is being prepared;   (b) Designed such internal control over financialreporting, or caused such internal control overfinancial reporting to be designed under oursupervision, to provide reasonable assurance regardingthe reliability of financial reporting and thepreparation of financial statements for externalpurposes in accordance with generally acceptedaccounting principles;   (c) Evaluated the effectiveness of the registrant’sdisclosure controls and procedures and presented inthis report our conclusions about the effectiveness ofthe disclosure controls and procedures, as of the endof the period covered by this report based on suchevaluation; and   (d) Disclosed in this report any change in the registrant’sinternal control over financial reporting that occurredduring the registrant’s most recent fiscal quarter (theregistrant’s fourth fiscal quarter in the case of anannual report) that has materially affected, or isreasonably likely to materially affect, theregistrant’s internal control over financial reporting;and 5. The registrant’s other certifying officer and I have disclosed,based on our most recent evaluation of internal control overfinancial reporting, to the registrant’s auditors and the auditcommittee of the registrant’s board of directors (or personsperforming the equivalent functions):  (a) All significant deficiencies and material weaknesses in thedesign or operation of internal control over financialreporting which are reasonably likely to adversely affectthe registrant’s ability to record, process, summarize andreport financial information; and   (b) Any fraud, whether or not material, that involves managementor other employees who have a significant role in theregistrant’s internal control over financial reporting.Date: August 9, 2005/s/ Thomas L. Monahan IIIThomas L. Monahan IIIChief Executive Officer