For the first time in history, psychiatrists during the Nazi era sought to systematically exterminate their patients. However, little has been published from this dark period analyzing what may be learned for clinical and research psychiatry. At each stage in the murderous process lay a series of unethical and heinous practices, with many psychiatrists demonstrating a profound commitment to the atrocities, playing central, pivotal roles critical to the success of Nazi policy. Several misconceptions led to this misconduct, including allowing philosophical constructs to define clinical practice, focusing exclusively on preventative medicine, allowing political pressures to influence practice, blurring the roles of clinicians and researchers, and falsely believing that good science and good ethics always co-exist. Psychiatry during this period provides a most horrifying example of how science may be perverted by external forces. It thus becomes crucial to include the Nazi era psychiatry experience in ethics training as an example of proper practice gone awry.