The patterns of pulmonary circulation were assessed by angiography in a series of 24 patients with right atrial isomerism (asplenia syndrome) and pulmonary atresia. Mean age at catheterization was 21.5 days (range 1 day-11 months). The pulmonary arteries were confluent in 22 cases (91.7%). Eighteen patients (75%) had ductus-dependent pulmonary circulation in presence of confluent pulmonary arteries, similar to cases of pulmonary atresia combined with complex congenital heart disease. The ductus appeared in continuity with the aortic arch, shaping an acute angle with the descending aorta, as in cases of pulmonary atresia with ventricular septal defect. A bilateral ductus was present in 5 cases (20.8%), 3 with confluent and 2 with nonconfluent pulmonary arteries. One patient presented multiple systemic collaterals to the lungs. All the other patients had normal arborization of the pulmonary arteries. Seven patients presented an obstructed total anomalous pulmonary venous connection: 4 in inferior vena cava and 3 in superior vena cava. These anatomical observations provide useful information for the surgical palliation of these anomalies and, probably, warrant pre-operative angiographic evaluation in all the patients with right atrial isomerism.