Fifty-two consecutive infants who received intravenous indomethacin, 0.2 mg/kg, were reviewed to determine factors associated with the occurrence of oliguria. Serum creatinine and concentration prior to indomethacin did not predict the occurrence of oliguria. A mean urine output of less than 4.5 mL/kg/hr prior to the administration of indomethacin was the only factor that we determined to be associated with a significant risk of oliguria. Two infants developed symptomatic oliguria and both had a pre-indomethacin urine output less than 1.5 mL/kg/hr.