This report presents a summary of the in-session workshop on the new market-based mechanism, which was held in Bonn, Germany, on 19 May 2012, pursuant to the mandate set out in decision 2/CP.17, paragraph 86. At the workshop, participants from Parties and admitted observer organizations shared information and their views on three topics (models for discussion, technical elements, and challenges associated with implementation), following a presentation by the secretariat. The Ad Hoc Working Group on Long-term Cooperative Action under the Convention may wish to take note of the information contained in this report when conducting its work programme to elaborate modalities and procedures for the new market-based mechanism, with a view to recommending a decision to the Conference of the Parties at its eighteenth session