Numerous studies have pointed out the frequent association of tetralogy of Fallot (TF) with other cardiovascular defects and coronary tree anomalies. We found cardiac defects in 181 (68%) out of 265 patients with TF investigated by catheterization and selective coronary angiography. These anomalies were isolated in 88 cases (49%) and associated with others in 93 patients. In the case of an isolated anomaly associated with TF, the coronary tree was involved in 37.5% and the cardiovascular system in the remaining 62.5%; in the case of two anomalies, the coronary system was involved in 66% of the patients and the cardiovascular apparatus in 34%; in the case of three or more anomalies, the coronary arteries were involved in 71% and the cardiovascular system in 29%. Anomalies in the course and/or distribution of coronary arteries were present in 96 patients (36%): 10 had a single coronary ostium, 13 a left anterior descending artery arising from the right coronary artery, one a circumflex artery arising from the right coronary artery. Small fistulas between coronary arteries and the pulmonary artery were found in 20 cases; anastomoses between coronary and bronchial arteries or right atrium in 42. In 39 patients we observed a large conus artery or large anterior ventricular branches crossing the right ventricle. A right aortic arch was found in 56 patients (21%), a stenosis of the trunk and/or the peripheral pulmonary artery in 35 (13%) and pulmonary artery atresia in five. Four patients showed a complete atrioventricular canal, three an atrial septal defect (primum type) with cleft of the mitral valve, 61 (23%) an atrial septal defect (ostium secundum). Eleven patients had anomalies of the systemic venous return, 26 (10%) a patent ductus arteriosus. Four patients had valvular abnormalities. In our series, a large proportion of cardiac defects associated with TF consists of anomalies of coronary arteries. Our data confirm the usefulness of performing preoperatively routine coronary angiography in patients with complex congenital heart disease.