We describe brain stem auditory evoked potentials (BAEP) obtained in 48 full-term newborns (20 boys, 28 girls) presenting with high serum total bilirubin concentration (from 238 to 442 mM) without Rhesus of group A, B, O factors incompatibility. Recordings were performed on the 3rd day of life and repeated 5-7 days post-appropriate therapy with photostimulation and exchange transfusion (when bilirubin concentration had decreased below 136 mM). Supplementary recordings were performed 3, 6 and 12 weeks later in order to assess test-retest reliability of components. Mean values of BAEP latencies were compared with those obtained in 40 age-matched control subjects using the same recording procedures. At first recording session (on the 3rd day), latencies of waves III and V obtained in hyperbilirubinemic patients were significantly increased as compared with records in control subjects. Recordings performed 5 to 7 days post-therapy and during subsequent recording sessions showed no significant differences between patients and control groups. Serial neuropsychological evaluations obtained over a 3-year follow-up showed no subsequent neurodevelopmental abnormality for all patients. These findings suggest that hyperbilirubinemia can alter central neurotransmission in auditory brain stem pathways, but this modification is only transient.