Book excerpt: Traces the development of racial hygiene theory and eugenics research in Germany from the end of the 19th century through the Third Reich. Discusses particularly the work of Alfred Ploetz, a leading propagator of racial hygiene, and his anti-Jewish views. It was argued that German medical science had fallen prey to the "Jewish spirit" and was thus in need of reform. Argues that the biological, medical, and anthropological variants of racism were not only concerned with antisemitism but also influenced Nazi health and social policy. Eugenicists of Jewish origin became victims of the system they had helped to construct. Analyzes how racial hygiene theories were incorporated into Hitler's racial antisemitism and became the basis for the Nazi sterilization and euthanasia programs which, in turn, became the basis for the mass murder of the Jews.