To test the hypotheses that administering dopamine before and concurrently with indomethacin therapy would (1) increase successful ductal closure rate, (2) act by maintaining a diuresis, and (3) prevent oliguria or high serum creatinine concentrations, we conducted a randomized, controlled trial in infants whose gestational age was <36 weeks and who had hemodynamically significant ductus arteriosus. Thirty-six infants were selected to receive a continuous infusion of either placebo or dopamine at either a low dosage of 2 μg/kg per minute or a higher dosage of 5 μg/kg per minute, beginning 6 hours before the use of indomethacin and continuing until 12 hours after the third dose of indomethacin. A total of 12 patients were selected to receive placebo, 14 were selected to recelve “low dopamine”, and 10 were selected to receive “high dopamine”. The three groups were similar in their initial characteristics. Serum creatinine concentrations, urine output, and fractional excretion of sodium were not different in the three groups after indomethacin treatment. Two patients receiving placebo required a second course of indomethacin compared with four patients in the low-dopamine group and one in the high-dopamine group. The proportion of failures of medical treatment was not statistically different among the three groups. We conclude that concomitant dopamine therapy neither decreases the failure rate in indomethacin-treated infants nor reduces the magnitude of the indomethacin-induced oliguria.