Prof Siep is the Chairman of the Central Committee for Stem-Cell-Research in Berlin and Member of the Board of the German Reference Center of Bioethics (DRZE) in Bonn. He has served on several committees in Bioethics, among them the Ethics Council of the German Federal Ministry of Health (1999-2002) and the Central Ethics Committee at the Chamber of the German Medical Council (1995-2004). Prof. Siep is member of several Scientific Academies, among them the Academies of Sciences in Northrine-Westphalia and Bavaria (corresponding member) and the German Academy for Ethics in Medicine. He published five books, more than 130 papers, and is the author of various articles in daily newspapers and magazines.