In an attempt to visualize the pulmonary arterial trees of neonates and infants with ductus-dependent decreased pulmonary flow, the efficacy of retrograde injection of contrast from the radial arteries of 11 consecutive patients was tested. All patients had pulmonary atresia and patent ductus arteriosus. A 22- or 24-gauge needle was inserted into the radial artery and contrast medium of 2 ml/kg was injected at flow rates of 3 to 4 ml/sec. The pulmonary arteries were filled by retrograde flow through the ductus arteriosus. This method provided clear visualization of the pulmonary arteries, especially by ductus-sided injections. Developmental anomalies of the pulmonary trunk, localized stenosis at the ductus, and aortopulmonary collateral arteries were demonstrated. No complications occurred during angiography, and all the procedures were completed within 30 minutes. This method appears to be useful in detecting anatomical abnormalities of the pulmonary arteries in neonates and infants with ductus-dependent decreased pulmonary flow.