The beta-antagonistic agent propranolol is increasingly being used in clinical trials for the prophylaxis and treatment of post-traumatic stress disorder (PTSD). This article discusses the evidence for the effectiveness of propranolol in the prophylaxis and treatment of PTSD and the ethical implications of research on these treatment approaches. The efficacy of a prophylactic or therapeutic use could not be shown during the last decade. Both treatment approaches raise ethical questions that should already be addressed during the clinical trials.