OBJECTIVE--To identify coronary artery anomalies in patients with tetralogy of Fallot with an aortogram taken with steep caudal and left oblique angulation ("end-on" aortogram). DESIGN--Prospective evaluation of end-on aortogram in the preoperative angiographic assessment of consecutive patients with tetralogy of Fallot. SETTING--Regional paediatric cardiology centre. PATIENTS--34 patients, aged 3 months to 12 years (median age 9 months). METHODS--An aortogram was performed with steep caudal (38 degrees-45 degrees) and left oblique (0 degrees-30 degrees) angulation under general anaesthetic as part of routine preoperative angiographic assessment. RESULTS--The origins and courses of the coronary arteries were visualised in all patients and important coronary artery anomalies were identified in four patients: single left coronary artery; single right coronary artery (two patients); separate high origin of left anterior descending. These anomalous coronary vessels crossed the right ventricular outflow tract. CONCLUSIONS--It is important to identify preoperatively coronary arteries that may interfere with right ventricular outflow tract reconstruction. An aortogram with steep caudal and left oblique angulation is useful in identifying anomalous coronary arteries and more importantly it defines the relation of these vessels to the right ventricular outflow tract.