We examined the pertinent surgical features of the anatomy of 56 hearts having tetralogy of Fallot with pulmonary atresia instead of stenosis, or malformations with pulmonary atresia closely related to tetralogy. We took particular cognizance of the pulmonary arterial supply in 15 hearts in which this was derived through systemic-to-pulmonary collateral arteries, dissecting, as far as possible, the bronchopulmonary segmental distribution of the collateral arteries compared to the intrapericardial pulmonary arteries in 11 of these hearts. Two of the hearts had absence of intrapericardial pulmonary arteries, so that a solitary arterial trunk left the base of the heart. Evidence of an atretic subpulmonary infundibulum was found in 40 of the hearts, while such an infundibulum was lacking in the remainder. The pulmonary atresia was muscular in 43 hearts, valvar in 11, while the pulmonary trunk was absent in the other two hearts. In the hearts with collateral arteries, on average 2.6 collaterals were found in each case, varying from two to five per case. Only one of these arose from a brachiocephalic artery, the others all arising from the descending aorta. The distribution of collateral arteries in two cases was remarkably reminiscent of the arrangement of bronchial arteries. As far as could be judged, 16.5 bronchopulmonary segments on average were supplied in each heart, 5.1 exclusively by collateral arteries, 11.8 by intrapericardial pulmonary arteries and an average of 0.64 segments per case having a shared supply.