Geographic variations in the incidence of different congenital coronary anomalies are well known, but infrequently studied in the Indian population. Among 4,100 adult patients who underwent diagnostic coronary arteriography, 39 (0.95%) patients (34 males, 5 females) had one or more anomalous coronary arteries. Their mean age was 46.4 +/- 8.2 years (range, 26-68 years). Thirty-five (89.74%) had anomalies of origin and distribution, while the remaining four (10.25%) had coronary artery fistulae. Right coronary artery was the commonest anomalous vessel, involved in 19 (48.74%) patients. It was originating from the left sinus of Valsalva in 15 and from the non-facing aortic sinus in four patients. Anomalous left circumflex artery was the second commonest anomaly, seen in 14 (35.89%) patients. Anomalous left anterior descending artery and anomalous left coronary artery from pulmonary artery were seen in one patient each. Among patients with coronary fistulae, two had fistulae between the left anterior descending artery and the main pulmonary artery, one between the conal artery and the right atrium, while the fourth patient had fistulae from the right coronary as well as from the left anterior descending artery to the left atrium. Atherosclerotic plaques in the anomalous arteries were seen in only 13 (33.33%) patients, much less than the overall incidence of coronary artery disease in patients with congenital coronary anomalies in this series (66.66%). In four (10.25%) patients, only the anomalous vessels were involved in coronary artery disease. Thus, in a small subgroup there does not appear to be an increased risk for development of atherosclerotic coronary artery disease in anomalous coronary arteries. Recognition of coronary anomalies is important in patients undergoing coronary arteriography, coronary interventions and cardiac surgery. Variations in the frequency of primary congenital coronary anomalies may possibly have a genetic background.