This note synthesizes the work undertaken by the Subsidiary Body for Scientific and Technological Advice (SBSTA) under its agenda item on scientific, technical and socio-economic aspects of mitigation. It covers the activities and discussions that have taken place since the adoption of the agenda item by the SBSTA at its twentieth session, including information presented during eight in-session workshops. Relevant submissions of views from Parties under this agenda item have also been taken into consideration. The information in the note is grouped according to two periods of work: identification of, and information-sharing on, framing issues; and information-sharing on specific sectors. The note highlights mitigation activities undertaken in the following thematic areas: mitigation planning, measures and actions; mainstreaming mitigation into sustainable development; and technology cooperation. In addition, it underlines scientific, technical and socioeconomic aspects of mitigation actions in specific sectors, such as agriculture, energy, forestry, industry, transport and waste management, and specific to non carbon dioxide gases