The incidence of symptomatic patent ductus arteriosus (sPDA) in very-low-birth-weight infants has been reported almost exclusively from referral centers. Moreover, the incidence has varied considerably. We prospectively evaluated the incidence and risk factors of sPDA in a totally inborn population of infants less than or equal to 1500 g birth weight (n = 120) receiving conservative fluid management and examined the role of echocardiography in predicting sPDA before clinical signs are evident. The incidence of sPDA was relatively low (16%) and the age at onset was relatively late (mean +/- S.E. = 14.7 +/- 3.0 days) when compared to prior reports. Echocardiographic changes preceded physical and radiographic findings of sPDA. Fluid volume within the range administered to our infants was unrelated to the occurrence of sPDA. However, risk factors identifiable within 24 h of birth were defined: obstetric estimate of gestational age, race, mean fluid volume intake in the initial 24 h, and early treatment with volume expanders. From these risk factors, 79% of infants with sPDA and 79% without sPDA could be predicted by stepwise discriminant function analyses. These findings may be employed in studies needed to assess the benefit of early surgical or pharmacologic therapy for infants at highest risk for sPDA.