Early treatment of premature infants with indomethacin has been proposed as a means of reducing the morbidity associated with respiratory distress syndrome complicated by symptomatic patent ductus arteriosus. We identified 26 infants less than 48 hours old with severe respiratory distress syndrome who had an asymptomatic patent ductus arteriosus. These infants were treated with either indomethacin or placebo. There was a significant difference in the frequency of ductal closure after receiving indomethacin treatment. No significant difference was observed in the time required for mechanical ventilation, time receiving supplemental oxygen, or time in the hospital, and there were no significant differences in the incidence of bronchopulmonary dysplasia, intraventricular hemorrhage, retinopathy of prematurity, or death between the two groups.