Coronary artery anomalies in 126,595 patients undergoing coronary arteriography. Coronary artery anomalies were found in 1,686 patients (1.3% incidence) undergoing coronary arteriography at the Cleveland Clinic Foundation from 1960 to 1988. Of the 1,686 patients, 1,461 (87%) had anomalies of origin and distribution, and 225 (13%) had coronary artery fistulae. Most coronary anomalies did not result in signs, symptoms, or complications, and usually were discovered as incidental findings at the time of catheterization. Eighty-one percent were "benign" anomalies: 1) separate origin of the left anterior descending and circumflex from the left sinus of Valsalva; 2) ectopic origin of the circumflex from the right sinus of Valsalva; 3) ectopic coronary origin from the posterior sinus of Valsalva; 4) anomalous coronary origin from the ascending aorta; 5) absent circumflex; 6) intercoronary communications; and 7) small coronary artery fistulae. Other anomalies may be associated with potentially serious sequelae such as angina pectoris, myocardial infarction, syncope, cardiac arrhythmias, congestive heart failure, or sudden death. Potentially serious anomalies include: 1) ectopic coronary origin from the pulmonary artery; 2) ectopic coronary origin from the opposite aortic sinus; 3) single coronary artery; and 4) large coronary fistulae. Coronary artery anomalies require accurate recognition, and at times, surgical correction. 