Clinical and necropsy findings are described in 10 patients in whom the right coronary artery arose from the left coronary sinus and then passed to the right atrioventricular (A-V) sulcus by coursing between the aorta and the pulmonary trunk. In 7 of the 10 patients, the coronary anomaly never caused symptoms of cardiac dysfunction. In the other three, all of whom died suddenly, the coronary anomaly was the only significant abnormality found at necropsy: One patient had recurring ventricular tachycardis, one had typical angina pectoris and, in one, sudden death was the initial manifestation of cardiac dysfunction. Review of previous angiographic studies during life of 31 patients reported to have origin of the right coronary artery from the left sinus of Valsalva indicated that 9 had symptoms of cardiac dysfunction in the absence of intraluminal coronary narrowing or associated noncoronary cardiac disease. Thus, origin of the right coronary artery from the left sinus may produce cardiac dysfunction that can be fatal.