Among 13010 adults who underwent coronary arteriography, 80 (0.61%) patients had a total of 83 anomalous coronary arteries. Thirty-three (41%) of the patients were of Hispanic origin, while out of the entire population studied 30% were Hispanic. The right coronary artery was the most common anomalous vessel. It was identified in 50 (62%) patients, arising in 35 from the left aortic sinus, in 14 from the posterior sinus, and in 1 from the left coronary artery. An anomalous circumflex artery was recognized in 22 (27%) patients. Nine (11%) patients presented an anomalous left anterior descending artery, 1 patient an anomalous left main coronary artery, and another an anomalous septal perforator artery. Twenty-three (29%) patients had concomitant congenital heart abnormalities, most commonly. bicuspid aortic valve and mitral valve prolapse. In each of 5 patients with complex congenital heart disease the course of the anomalous vessel could have interfered with a surgical procedure. In 4 cases anomalous coronary arteries were associated with either anomalous systemic venous circulation or anomalous cardiac veins. In 5 (6%) patients only, the anomalous coronary artery was solely responsible for a clinical event. Coronary atherosclerosis of the anomalous arteries was found in 28% of the patients, while the overall incidence of the disease in this series was 65%. Thus, anomalous coronary arteries are associated with a high incidence of congenital heart diseases, but do not appear to be associated with an increased risk for development of coronary atherosclerosis. The angiographic recognition of these vessels is important in patients who undergo coronary angioplasty or cardiac surgery. Variations in the frequency of congenital coronary anomalies as reported herein may be attributed to a genetic background.