A left anterior descending coronary artery arising from the right coronary artery can be easily injured during performance of a right ventriculotomy for correction of tetralogy of Fallot. This occurred in 2 of the 23 patients in this series, and both patients died from myocardial failure in the early period after operation. Of 19 patients who presented a combination of tetralogy of Fallot and unusual coronary artery distribution, injury to the abnormal coronary artery was avoided by a transverse right ventriculotomy either alone or combined with an upper vertical incision in 17 patients. In 2 patients a Dacron tube graft was inserted between the right ventricular outflow tract and the pulmonary artery. In 2 patients a right ventriculotomy was avoided by closing the ventricular septal defect through a transaortic approach. All 21 patients survived. Before a vertical or longitudinal incision in the right ventricular outflow tract is performed, the coronary artery distribution should always be checked and confirmation made of the normal origin of the left anterior descending branch from the left coronary artery to the left of the pulmonary artery.