This report covers the work undertaken by the Executive Board of the clean development mechanism (CDM) from 23 September 2017 to 31 August 2018. Work focused on further simplifying the mechanism and promoting its use in the international response to climate change. The reporting period saw a decrease in project registrations and issuance of certified emission reductions (CERs) compared with the previous reporting period. Demand for the CDM and its CERs remains low compared with demand in the first commitment period of the Kyoto Protocol, which ended in 2012. This report includes a recommendation for action and a request for overall guidance from the Conference of the Parties serving as the meeting of the Parties to the Kyoto Protocol at its fourteenth session. During the reporting period the Board held its 100^th meeting and took the opportunity to reflect on the achievements of the CDM, which are described in an online publication launched at that meeting.