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Introduction: Whether the severity of bilirubin neurotoxicity is closely related to the level of total serum bilirubin (TSB) remains to be determined.Materials and Methods: We studied the amplitudes of brainstem auditory evoked response (BAER) components in 83 term neonates with TSB >10 mg/dL to detect any differences in bilirubin ototoxic effect on the amplitudes between different levels of TSB.Results and Discussion: Compared to age-matched normal controls, the amplitudes of BAER waves III and V were reduced significantly (P<0.01 and 0.001). The V/I and V/III amplitude ratios were also decreased significantly (P<0.001 and 0.01). Although all amplitudes tended to be lower at higher TSB levels than at lower levels, none of the amplitudes correlated significantly with the level of TSB. Neither the V/I amplitude ratio nor the V/III amplitude ratio correlated with the TSB. No significant differences were found in any BAER wave amplitudes among the TSB levels 11-15, 16-20 and >20 mg/dL. In the comparison of amplitude data between any two of the three TSB levels, only wave V amplitude showed significant difference between TSB levels 11-15 and >20 mg/dL (P < 0.05).Conclusion: BAER wave amplitudes were significantly reduced in neonates with hyperbilirubinemia. However, there was no close correlation between the degree of amplitude reduction and the level of TSB. These results indicate that bilirubin toxicity to the neonatal brain is not closely related to the level of TSB. [ABSTRACT FROM AUTHOR]