Randomization is the "gold standard" design for clinical research trials, and is accepted as the best way to reduce bias. Although some controversy remains over this matter, we believe equipoise is the fundamental ethical requirement for conducting a randomized clinical trial. Despite much attention to the ethics of randomization, the moral psychology of this study design has not been explored. This paper analyzes the ethical tensions that arise from conducting these studies, and examines the moral psychology of this design from the perspectives of physician-investigators and patient-subjects. We conclude with a discussion of the practical implications of this analysis.