Ethics and epistemology in medicine are more closely and more interestingly intertwined than is usually recognized. To explore this relationship, I present a case study, clinical trials of extracorporeal membrane oxygenation (ECMO; an intervention for persistent pulmonary hypertension of the newborn).Three separate ethical issues that arise from this case study-whether or not it is ethical to perform a certain trial at all, whether stopping rules for trials are ethically mandated, and the issue of informed consent-are all shown to be intimately related to epistemological judgments about the weight of evidence. Although ethical issues cannot, of course, be resolved by consideration of epistemological findings, I argue that no informed view o...