Ligation of a patent ductus arteriosus was carried out in 22 premature infants, 20 with concomitant respiratory distress. The duration of high-volume shunting is critical in determining the prognosis for these infants. Because of the low surgical mortality and morbidity and the high incidence of bronchopulmonary dysplasia in babies managed conservatively, infants with respiratory distress syndrome (RDS) who are respirator dependent should undergo ligation as soon as the presence of large left-to-right shunting is detetmined. Premature infants without RDS or those with mild RDS who are not respirator dependent can be managed medically or with elective ligation. Surgical intervention is strongly indicated in patients with persistent congestive heart failure and respiratory failure. Echocardiography offers an accurate and risk-free approach to the early diagnosis of a large left-to-right shunt through the ductus.