**Exhibit 31.1****CERTIFICATION**I, Thomas L. Monahan III, certify that:1. I have reviewed this annual report on Form 10-K/A of The Corporate Executive Board Company; 2. Based on my knowledge, this report does not contain any untrue statement of a material fact oromit 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 the periodcovered by this report; 3. Based on my knowledge, the financial statements, and other financial information included in thisreport, fairly present in all material respects the financial condition, results of operationsand cash flows of the registrant as of, and for, the periods presented in this report; 4. The registrant’s other certifying officer and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) andinternal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and15(d)-15(f)) for the registrant and have: a) Designed such disclosure controls andprocedures, or caused such disclosurecontrols and procedures to be designed underour supervision, to ensure that materialinformation relating to the registrant,including its consolidated subsidiaries, ismade known to us by others within thoseentities, particularly during the period inwhich this report is being prepared;  b) Designed such internal control over financialreporting, or caused such internal controlover financial reporting to be designed underour supervision, to provide reasonableassurance regarding the reliability offinancial reporting and the preparation offinancial statements for external purposes inaccordance with generally accepted accountingprinciples;  c) Evaluated the effectiveness of theregistrant’s disclosure controls andprocedures and presented in this report ourconclusions about the effectiveness of thedisclosure controls and procedures, as of theend of the period covered by this reportbased on such evaluation; and  d) Disclosed in this report any change in theregistrant’s internal control over financialreporting that occurred during theregistrant’s most recent fiscal quarter (theregistrant’s fourth fiscal quarter in thecase of an annual report) that has materiallyaffected, or is reasonably likely tomaterially affect, the registrant’s internalcontrol over financial reporting; and5. The registrant’s other certifying officer and I have disclosed, based on our most recentevaluation of internal control over financial reporting, to the registrant’s auditors and theaudit committee of the registrant’s board of directors (or persons performing the equivalentfunctions): a) All significant deficiencies and materialweaknesses in the design or operation ofinternal control over financial reportingwhich are reasonably likely to adverselyaffect the registrant’s ability to record,process, summarize and report financialinformation; and  b) Any fraud, whether or not material, thatinvolves management or other employees whohave a significant role in the registrant’sinternal control over financial reporting.Date: May 1, 2006   /s/ Thomas L. Monahan III      Thomas L. Monahan III  Chief Executive Officer