OBJECTIVE: To study the value of a new technique, maximum length sequences brainstem auditory evoked potential (MLS BAEP), in the assessment of the severity of brain damage following asphyxia in term neonates. METHODS: One hundred and three neonates with perinatal asphyxia and 26 normal term neonates were eligible for the study. Conventional and MLS BAEP examinations were performed within three days after birth. Of the 103 neonates with asphyxia, 17 did not suffer from HIE, 37 had mild HIE, 31 had moderate HIE, and 18 had severe HIE. The latencies and amplitudes of waves I, III and V, and the inter-peak intervals of I-III, III-V, and I-V were analyzed. RESULTS: The latencies of wave V and the inter-peak intervals of I-III, III-V and I-V prolonged gradually with the more severe HIE in both the MLS and the conventional BAEP (P<0.05 or 0.01). The differences among groups were more significant with the increasing repetition rate of click in the MLS BAEP. Compared with the normal controls, conventional BAEP did not show prolonged intervals of I-III and III-V in the mild HIE subgroup, and a prolonged inter-peak interval of III-V in the moderate HIE subgroup, while the MLS BAEP showed significantly prolonged inter-peak intervals of I-III and III-V in the three HIE subgroups and the differences were more and more significant as an increase in the repetition rate of click from 91 to 910 times/seconds. CONCLUSIONS: MLS BAEP is more sensitive and valuable than the conventional one in detecting hypoxic-ischemic brain damage following asphyxia by increasing the repetition rate of click. MLS BAEP provides a new measurement in quantity to assess the severity of HIE in neonates with perinatal asphyxia.