This report covers the work of the Executive Board of the clean development mechanism (CDM) during the period from 15 October 2010 to 26 October 2011, during which the CDM saw continued growth and the Board and its support structure undertook a wide range of work to enhance the mechanism. There are now more than 3,500 registered projects in 72 countries and a further 3,600 plus projects in the registration pipeline (from validation stage). In addition, there are 13 registered programmes of activities (PoAs) in 11 countries with a total of 1,103 component project activities and 26 PoAs in the registration pipeline. 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