This report covers the work of the Executive Board of the clean development mechanism (CDM) during the period from 17 October 2009 to 14 October 2010, during which the CDM saw continued growth and the Board and its support structure undertook a wide range of work to enhance the mechanism. Over the reporting period, the Board finalized 631 requests for registration and 588 requests for issuance. There are now more than 6,300 CDM project activities (registered projects and those seeking registration), including some 962 component project activities registered under a programme of activities during the reporting period. Were all of the registered projects to deliver their estimated emission reductions, about 1.84 billion certified emission reductions would be generated during the first commitment period of the Kyoto Protocol. The report highlights achievements and challenges faced by the Board in its supervision of the mechanism. It also highlights work undertaken in the areas of accreditation, methodologies and registration and issuance. Further, it includes a number of recommendations for action by the Conference of the Parties serving as the meeting of the Parties to the Kyoto Protocol