Hans Troidl, director of the surgical clinic at Cologne-Merheim and a professor of surgery at the University of Cologne, was a pioneer of endoscopic surgery. He was born on 5 July 1938 in Schwarzenfeld, Bavaria, Germany, and studied medicine in Munich from 1959 to 1964. He subsequently trained in general medicine in Munich under Rudolf Zenker, and in Marburg and Kiel with Horst Hamelmann. In 1981 he was appointed to his post in Cologne, a role he held until his retirement in 2003. He was a visiting professor in Canada at McGill and Montreal universities, and in the United States at Creighton University, Omaha, and Virginia Commonwealth University, Richmond. He was the co-editor of *Surgical Endoscopy, Ultrasound and Interventional Techniques*, which he founded, *Endoscopy*, *European Journal of Surgery – Beyond the Scalpel*, *Langenbeck’s Archives of Surgery* and *‘MIC’ Minimally Invasive Surgery*. He co-edited the textbook *Surgical research: basic principles and clinical practice*, which ran to three editions, originally published as *Principles and practice of research: strategies for surgical investigators* (New York, Springer, 1987), and wrote more than 200 papers as the first author, including on controlled clinical trials, quality of life, endoscopy and ultrasound, endoscopic surgery, flexible endoscopy, surgical research and the philosophy of science. He lectured nationally and internationally, and was a member of the Société Internationale de Chirurgie, the Surgical Infection Society Europe, the American College of Surgeons and the European Association of Endoscopic Surgery, of which he was the founding president. He was an honorary fellow of the American College of Surgeons, the Association Française de Chirurgie and of the Royal College of Surgeons of England. In 1997 he was awarded the Erich Lexer prize in Munich. He enjoyed reading philosophy, epistemology and the philosophy of science, and ‘Discussions…with philosophers, evolutionary biologists, theologians, physicists, lawyers, managers and journalists’, classical music, good food and drink, and travel, particularly to Italy and France. He married Ulla in 1963. They had four children and nine grandchildren. Troidl died on 31 January 2020. He was 81.