The Twenty-first Session of the Scientific Advisory Committee of the Acid Deposition Monitoring Network in East Asia (SAC21) was organised virtually from 26-28 October 2021, to discuss scientific and technical matters related to the EANET activities. Over 60 members of the Scientific Advisory Committee and/or their representatives from the Participating Countries of the EANET joined the meeting. The Draft EANET Data Report 2020 was adopted showcasing different results and trends in the region since 2000. In addition, the Draft Report on the Inter-laboratory Comparison (ILC) Projects 2020 and the overview of the National Monitoring Plans of the Participating Countries for 2021 were also presented. At the meeting, the SAC21 members were invited to share their comments, from the scientific viewpoint, on the draft Annex to the EANET Instrument, for consideration and approval at the IG23 of EANET, in November 2021. The AIT RRC.AP had actively participated and greatly supported in the organisation of the EANET SAC21 meeting. More information.