A major coronary artery crossing the right ventricular outflow tract in patients with tetralogy of Fallot interferes with a transannular patch, and preoperative detection of this artery is important. We evaluated the ability of two-dimensional echocardiography to define noninvasively the coronary artery anatomy in 37 consecutive patients (age range, 1 day to 18 years; mean age, 40.9 months). The origin and distribution of the right anterior descending and circumflex coronary arteries, as well as any anteriorly coursing vessel, were examined from parasternal views. Complete studies were obtained in 29 (78%) of the 37 patients. Coronary artery anatomy was determined to be normal by echocardiography in 20 (69%) of the 29 patients. An anterior vessel across the right ventricular outflow tract was detected in the remaining nine patients. Six patients had an anterior descending artery from the left main coronary artery (paired anterior descending arteries in three patients, a right anterior descending artery from the left main coronary artery in two patients, and a right coronary-to-pulmonary artery fistula in one patient). Three patients had no anterior descending artery from the left main coronary artery (anterior descending artery from the right main coronary artery in two patients, and anterior descending and circumflex arteries from the right main coronary artery in one patient). Angiography, surgery, or autopsy confirmed the diagnoses in all but the final patient in whom the anterior descending artery arose from the right main coronary artery as observed at surgery, but the circumflex artery was not seen. Accurate evaluation of coronary artery anatomy is possible by echocardiography in the majority of patients with tetralogy of Fallot. Noninvasive identification of a major coronary artery coursing anteriorly can influence the timing of cardiac catheterization and surgery and the need for angiography.