**Exhibit 31.1****CERTIFICATION**I, Thomas L. Monahan III, certify that:1. I have reviewed this annual report on Form 10-K of The Corporate Executive Board Company; 2. Based on my knowledge, this report does not contain any untrue statement of a materialfact or omit to state a material fact necessary to make the statements made, in light ofthe circumstances under which such statements were made, not misleading with respect tothe period covered by this report; 3. Based on my knowledge, the financial statements, and other financial informationincluded in this report, fairly present in all material respects the financialcondition, results of operations and cash flows of the registrant as of, and for, theperiods presented in this report; 4. The registrant’s other certifying officer and I are responsible for establishing andmaintaining disclosure controls and procedures (as defined in Exchange Act Rules13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined inExchange Act Rules 13a-15(f) and 15(d)-15(f)) for the registrant and have: a) Designed such disclosure controls and procedures, or causedsuch disclosure controls and procedures to be designedunder our supervision, to ensure that material informationrelating to the registrant, including its consolidatedsubsidiaries, is made known to us by others within thoseentities, particularly during the period in which thisreport is being prepared;  b) Designed such internal control over financial reporting, orcaused such internal control over financial reporting to bedesigned under our supervision, to provide reasonableassurance regarding the reliability of financial reportingand the preparation of financial statements for externalpurposes in accordance with generally accepted accountingprinciples;  c) Evaluated the effectiveness of the registrant’s disclosurecontrols and procedures and presented in this report ourconclusions about the effectiveness of the disclosurecontrols and procedures, as of the end of the periodcovered by this report based on such evaluation; 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 an annualreport) that has materially affected, or is reasonablylikely to materially affect, the registrant’s internalcontrol over financial reporting; and5. 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 affect theregistrant’s ability to record, process, summarize and reportfinancial 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: February 27, 2006     /s/ Thomas L. Monahan III        Thomas L. Monahan III  Chief Executive Officer