We studied the effects of hyperbilirubinemia on brainstem auditory pathways and neurodevelopmental status in 99 fullterm neonates with severe nonhemolytic hyperbilirubinemia (total serum bilirubin level = 301 to 500 µmol/L) born between 1995 and 2000. These were divided into three groups: group 1, moderate hyperbilirubinemia ( n = 30; mean maximum total serum bilirubin = 320.7 µmol/L or 18.9 mg%); group 2, severe hyperbilirubinemia ( n= 63; mean maximum total serum bilirubin = 369.0 µmol/L or 21.7 mg%); and group 3, super hyperbilirubinemia ( n = 6; mean maximum total serum bilirubin = 457.2 µmol/L or 26.9 mg%). All received phototherapy, and three neonates also had exchange transfusion. Initial brainstem auditory evoked potentials were recorded in all at the mean age of 3.1 months (range 1—9 months). At initial assessment, only nine neonates (9.1%) had abnormal brainstem auditory evoked potentials. All except two returned to normal at 2 years. These two children had a hearing threshold at 50 nHL. We then compared serial brainstem auditory evoked potentials until 2 years for these nine cases with initial abnormal brainstem auditory evoked potentials, and nine cases with initial normal brainstem auditory evoked potentials were recruited for comparison. All 99 children had regular physical, neurologic, visual, and auditory assessments every 3 to 6 months until the age of 3 years. There was no significant correlation between demographic factors (gender, gestational age, or birthweight), maximum total serum bilirubin, and total serum bilirubin at discharge with an abnormal brainstem auditory evoked potential. There was no significant difference in the rate of brainstem auditory evoked potential abnormalities between the three groups: moderate (10%), severe (7.9%), and super (16.7%). All had normal neurodevelopmental status at 3 years. Only two children had transient mild motor delay and hypotonia, and both had normal brainstem auditory evoked potentials. There was no relationship between the abnormalities of the brainstem auditory evoked potentials and neurodevelopmental status. None of the three children receiving exchange transfusion had abnormal brainstem auditory evoked potentials or neurodevelopmental outcome. With the neurophysiologic and clinical outcomes in our cohort with severe nonhemolytic hyperbilirubinemia, we propose that the toxic effect of hyperbilirubinemia on auditory brainstem pathways might be transient provided that prompt treatment is initiated. ( J Child Neurol 2006;21:309—315; DOI 10.2310/7010.2006.00058).