The Fourth International Symposium on Anaerobic Digestion was held from November 11 through November 1985. The plenary lectures were divided into five subject categories: Biogas: Chinese experiences; Science-up-todate: Agricultural Applications, Industrial Applications, Global activities. The report reviews teh symposium ainly from two aspects, Industrial reactor Applications and Basic Research. The UASB-reactor dominated the industrial applications. Few, if any, novel reactor designs were presented Among questions discussed were start-up technics for UASB-reactors and anaerobic filters, and sulphate and suphide inhibition. Lectures an posters on Basic Research dealt mainly with microbiological questions or studies on toxicity and inhibitio. Report in Swedish