Coronary angiograms of 296 patients with Fallot's tetralogy were reviewed. Group I abnormalities in the origin and distribution of the coronary arteries, found in 32 (11.8%) cases, consisted of a single coronary artery from the left sinus of Valsalva in 7 cases, left anterior descending artery from the right coronary artery in 7 cases, and an accessory left anterior descending from the right coronary in 18 cases. Of the 7 cases with a single coronary artery, the right coronary branch was anterior to the aortic root, crossing the right ventricular outflow in two cases. Group II acquired abnormalities were found in 11 cases and consisted of an enlarged conus artery in 9 cases and 1 case each of coronary bronchial collateral and right ventricular branch from the left anterior descending artery. Except in 12 patients requiring selective coronary angiography, aortic root angiography was sufficient to outline the coronary anatomy. Awareness of a coronary anomaly helps in deciding the time and type of operative procedure to be performed, especially in infants, since injury to a large vessel perfusing the left ventricle usually results in increased morbidity and mortality.