To evaluate the results of ductal occlusion with the Rashkind prosthesis, 78 children (group 1, 19 boys and 59 girls; mean age at occlusion, 4.5 +/- 4.0 years) with isolated patent ductus arteriosus (n = 73) or in association with other lesions (n = 5) were evaluated by pulsed and color flow Doppler 9 +/- 7 months (range, 2-26 months) after occlusion. Thirty children who had undergone patent ductus arteriosus ligation (group 2, 9 boys and 21 girls; mean age at study, 5.7 +/- 4.9 years; mean follow-up after ligation, 44 +/- 58 months) were evaluated in the same way. The prevalence of residual ductal shunting and the main pulmonary arterial flow patterns were recorded. Residual ductal shunting in group 1 was 38% on day 1, decreasing slowly to 31% at 3 months, 27% at 6 months, and 19.7% at 1 year or more due to further spontaneous shunt resolution. The residual shunting rate in group 2 (6%) was significantly lower than that at 1 year or more in group 1 (p less than 0.001). Successful reocclusion in 5 of 6 in a subset of patients in group 1 followed for 1 year or less reduced further the prevalence of residual shunting. Residual shunting after patent ductus arteriosus occlusion is more common than after ligation, but continues to decrease during follow-up.