Among 7.000 patients who underwent diagnostic coronary arteriography at Hahnemann Medical College and Hospital, we found 45 patients (0.64%) with anomalous aortic origin of one or more coronary arteries. There were 31 men (69%) and 14 women (31%). The patients were classified into the following groups: 1) anomalous origin of the circumflex coronary artery (26 patients, 57.8%); 2) both coronary arteries arising from the left sinus of Valsalva (12 patients, 26.7%); 3) both coronary arteries arising from the right sinus of Valsalva (four patients, 8.9%); 4) anomalous origin of the left anterior descending coronary artery from the right sinus of Valsalva (two patients); and 5) anomalous origin of the first septal perforator from the right sinus of Valsalva (three patients); in one of these patients it was an isolated finding; and in the other two there were other anomalous vessels. Associated valvular heart disease was present in 14 patients (31%); coronary artery disease in 11 (24.5%); idiopathic hypertrophic subaortic stenosis in two; miscellaneous heart diseases in eight (17.8%); and no heart disease in 11 (24.5%). Angina pectoris was present in 42.2%; atypical chest pain in 28.9%; syncope in 17.7%; palpitations in 46.7%; and a history of hypertension in 40%. We conclude that 1) anomalous coronary arteries are associated with a high incidence of hypertension and valvular heart disease in the sample of patients studied; 2) there was a high incidence of palpitations, but this and the other symptoms were difficult to evaluate because of the associated disease; 3) in certain patients with anomalous origin of the left main coronary artery (LM) from the right sinus of Valsalva, myocardial perfusion is probably impaired and may be associated with serious cardiac event whether the initial course of the LM is posterior to the aorta, between the aorta and the pulmonary artery, and/or anterior to the pulmonary artery. Course of the anomalous LM coronary artery between aorta and the pulmonary artery may be associated with sudden death. Atherosclerosis of a single coronary artery proximal to its branching is an additional liability to the anomaly. Since sudden death occurs most commonly in young individuals with anomalous origin of the LM, special care should be taken to evaluate young patients with chest pain resembling angina. A maximal treadmill exercise test should be performed first, and if there is evidence of ischemia, a coronary arteriogram should be performed. Recognition of anomalous origin of coronary arteries and their course also is important in patients undergoing surgery for aortocoronary bypass or for valvular heart disease when perfusion of coronary arteries is needed.