Based on a wealth of hitherto neglected archival sources, this study analyzes the origins, social composition and impact of eugenics in the context of the social and political tension of the rapidly industrializing Nazi empire. Until recently, historians of German racism have limited their analysis of the origins of the Holocaust to a handful of völkisch racial ideologies, overlooking the effects of racial ideas on biology, on the rapidly expanding medical profession and on public health services. Historians of medicine and social and political historians of modern Germany will be interested in this important book.