The purpose of this study was to investigate the effects of changes in renal function on gentamicin disposition following perinatal asphyxia. Gentamicin pharmacokinetics, renal function, mean arterial pressure (MAP) and five-minute Apgar scores were determined in 80 preterm infants admitted to two neonatal intensive care units over an 18 month period. A 2.5 mg/kg dose of gentamicin was infused intravascularly over 20 to 30 minutes in a retrograde fashion. The gentamicin half-life and clearance were prolonged in asphyxiated infants. For the asphyxiated infants gentamicin half-life increased and urine output decreased with a significant correlation (r = -0.66, p less than 0.05). Gentamicin clearance and urine output in the asphyxia group correlated with MAP (r = +0.67, p = 0.07). In non-asphyxia infants no such correlation was seen. This study does not distinguish between asphyxia-induced or gentamicin-induced nephrotoxicity following gentamicin therapy. We suggest that gentamicin concentrations be closely monitored in asphyxiated newborns who demonstrate compromised renal function.