The long-term effects of the superior vena cava-pulmonary artery anastomosis were evaluated in 15 patients a mean of 8.5 years postoperatively. There were eight patients with tricuspid atresia and seven with other complex anomalies. Ten patients underwent 133xenon ventilation scans and 99mtechnetium perfusion scans in the upright and suprine positions. Perfusion scans showed decreased perfusion of the right upper lobe which improved in the supine position. Shunt flow, measured by thermodilution in nine patients, was a mean of 1.7 L. per minute per square meter, with a mean superior vena caval pressure of 8 mm. Hg and a resistance of 3.0 units. Right and left pulmonary venous saturations were 94 and 96 percent, respectively, showing little intrapulmonary shunting. Venous collaterals were the major cause for shunt failure. Six patients underwent a left Blalock-Taussig shunt and division of venous collaterals a mean of 6 years after the Glenn shunt and are all doing well. The superior vena cava-pulmonary artery anastomosis did not result in progressive pulmonary deterioration in the patients studied. The staged treatment of tricuspid atresia by the Glenn shunt followed by a systemic-pulmonary artery shunt and ligation of venous collaterals gives prolonged effective palliation.