As a result of randomized assignment, 15 preterm infants weighing 1,500 gm or less at birth and who had a symptomatic PDA were treated according to a medical management protocol, and ten according to an early surgical closure protocol. All infants required mechanical ventilation at the time of study entry, which was one week after birth. Birth weight, gestational age, age at onset of congestive failure, age at study entry, and the initial morbidity of members of the two groups were similar. The nine surviving infants managed according to the surgical closure protocol were weaned from mechanical ventilation sooner, had a decreased need for digoxin and furosemide, achieved gastrointestinal function sooner, and had a smaller hospital bill than the 12 survivors of the medical management group. These results indicate that infants with a symptomatic PDA still requiring mechanical ventilation at one week after birth will benefit from surgical closure of the ductus at that time.