From January 1987 to December 1988, in 22 infants with PAVSD, the diagnostic results obtained with echocardiography (two-dimensional, Doppler, and color) were prospectively compared to the angiocardiographic findings. We classified into group 1 patients with confluent and good-sized pulmonary (greater than or equal to 3 mm) arteries, single ductus arteriosus, and normal pulmonary venous connections ("favorable pattern"). The other patients with PAVSD were classified into group 2 ("unfavorable pattern"). The intracardiac anatomy, the morphology of the pulmonary arteries, and the pattern of pulmonary blood supply and pulmonary venous connection were correctly identified with echocardiography in all but one patient, who was erroneously considered to be in group 2. No false-positive of the "favorable pattern" (group 1) was detected. Echocardiography is an effective tool in infants with PAVSD, in order to discriminate cases with "favorable" and "unfavorable" patterns of pulmonary arteries, pulmonary blood supply, and pulmonary veins. The first group with the "favorable pattern" may be considered for systemic-to-pulmonary shunt surgery without angiocardiography. Based on this experience from January to December 1989, four patients with this "favorable pattern" underwent a successful systemic-to-pulmonary artery shunt with an echocardiographic diagnosis alone.