It is debatable whether patients benefit directly from participation in a randomized clinical trial. We attempt to address this question for participants in the Cardiac Arrhythmia Suppression Trial (CAST) and the Antiarrhythmics Versus Implantable Defibrillators (AVID) studies. Survival rates were compared between eligible patients who enrolled in the trials and eligible patients who did not enroll, adjusting for baseline covariates. In CAST, despite that the active therapy was found to confer an almost threefold increased risk of death, survival was similar between the 3163 enrolled and the 1363 nonenrolled eligible patients. However, when patients were under study management, their risk of death was approximately 20% lower than when they left study management. In AVID, overall survival was similar between the 1016 enrolled and the 1246 nonenrolled eligible patients. However, mortality was substantially higher among patients not enrolled because the referring physician mandated the type of therapy. Overall these observational analyses suggest a net improvement in survival for the participants in these two trials.