The 11 young boys, whose arrival so shocked the prisoners of Sachsenhausen, had been earmarked for medical experiments to identify the pathogens of hepatitis. There had been human experiments on prisoners in nearly all concentration camps since the beginning of the war. Initially exclusively grown men were used as test subjects for such experiments, primarily Polish, Jewish, Soviet and German concentration camp inmates. Experiments with concentration camp prisoners began immediately after the beginning of the war in the autumn of 1939. When determining test subjects for a research project, the interests of two parties were affected: those of the experimenting physicians and those of the concentration camp command on site. The physicians were interested in obtaining healthy prisoners in a sound state of nutrition, so that their test results would not be influenced by sickness or weaknesses. This chapter describes the experiments of the three physicians on children, with main emphasis on Dr. Arnold Dohmen's experiments in Sachsenhausen.