The main interest of Dr. Clavien has been in several aspects of transplantation and liver surgery. Since 1994 he has run an active basic science laboratory funded through NIH and Swiss National Grants and other private and non-private sources. His areas of research include organ preservation, liver ischemia-reperfusion injury and liver regeneration, and pathogenesis of cancer, as well as outcome research with publication in Science, PNAS, Gastroenterology, Lancet, and NEJM. His laboratory made the discovery of serotonin as a key mediator of liver regeneration and pathogenesis of cancer (Science 2008). Dr. Clavien has also developed a simple and widely used system to evaluate complications after surgery, which holds his name. The impact of his research might be highlighted with an H factor of 97. He has been president of the European Surgical Association (ESA), European Hepatobiliary Association (E-AHPBA) and the Swiss Transplantation Society.