The history of German psychiatry is characterized not only by innovative thought in the tradition of Kraepelin and Jaspers, but also by the "euthanasia" program that resulted in the killing of more than 100,000 psychiatric patients and mentally handicapped people. Exemplified by the Psychiatric Department at the University of Heidelberg, the relation between psychiatric research and the systematic killing of patients during the time of National Socialism is analysed. The first part of the paper summarizes the historical background of the general condition of German psychiatry in the 1930s and 1940s. The second part gives an outline of the biography and work of Carl Schneider (1891-1946), head of the Psychiatric Department at Heidelberg until 1945. It can be shown that the call for intensive therapy for those patients who were to be reintegrated into society was connected with the killing of those who were considered to be beyond reach of any active therapeutic approach. This is also the context of C.Schneider's research program concerning mentally handicapped children. The historical reconstruction of research activities, drawing on the patients' files and other documents, reveals that out of 52 children who had been examined, 20 were killed in the asylum of Eichberg in order that their brains might be examined in Heidelberg. The findings are discussed in view of the ongoing historiographical debate on the relationship between the politics of National Socialism and contemporary science.