Concurrently controlled, randomized clinical trials play an important role in the validation of treatment and control measures of cardiovascular disease. As such trials have been carried to conclusion, a great deal has been learned not only about the treatment of the disease but also about the methodology of clinical trials. Seven recently completed clinical trials, the Coronary Drug Project, the Aspirin Myocardial Infarction Study, the Anturane Reinfarction Trial, the Hypertension Detection and Follow-Up Program and three drug trials of betablockers, are reviewed from the perspective of both their clinical and methodological significance.