This report covers the work of the Executive Board of the clean development mechanism (CDM) during the period from 20 October 2007 to 24 October 2008, during which the CDM grew steadily. An additional 0.4 billion certified emission reductions (CERs) are expected to be delivered by the end of the first commitment period of the Kyoto Protocol. The now nearly 4,200 CDM project activities are expected to deliver about 2.9 billion CERs of which 1.3 billion CERs are generated by 1,186 registered CDM project activities. The 437 CDM project activities that have reached the phase of issuance have generated more than 202 million CERs. Over the period, the Board considered 1,086 requests for registration and issuance resulting in 359 additional CDM project activities and issuance of 107,604,113 CERs. The report highlights achievements and challenges faced by the Board in its supervision of this mechanism. It highlights work undertaken in the areas of accreditation, methodologies, registration and issuance. It includes a number of recommended actions by the Conference of the Parties serving as the meeting of the Parties to the Kyoto Protocol