Functional integrity of the auditory brainstem was studied at term in babies born at 30 -36 wk of gestation using maximum length sequence brainstem auditory evoked response (MLS BAER). Compared with normal term babies, preterm babies who had perinatal complications showed a tendency of an increase in wave V latency and I-V and III-V intervals at all 91-910/s clicks, with statistical significance at higher rates. Wave V latency and I-V interval increased significantly at 455/s and 910/s. III-V interval increased at all click rates, which was more significant at higher rates. III-V/I-III interval ratio increased at most rates. Waves III and V amplitudes reduced significantly mainly at 455/s and 910/s. In preterm babies who had no perinatal complications, there were no major MLS BAER abnormalities except an increase in III-V interval at 91-910/s. By comparison, the preterm babies with perinatal complications had a significant increase in wave V latency, I-V and III-V intervals, and III-V/I-III interval ratio at 455/s and 910/s clicks. These results suggest that although there are no major abnormalities in brainstem auditory function in preterm babies without perinatal complications, the auditory brainstem, mainly the more central part, in preterm babies with perinatal complications is impaired, which becomes more apparent at very high stimulus rates. We conclude that preterm babies with perinatal complications are at high risk of central auditory impairment. The integrity of auditory system is the base for language and speech development and has a tremendous impact on cognitive development. Auditory impairment, if undetected, will impede speech, language, and cognitive development (1,2). Impairment of the central auditory system eliminates or modulates afferent activity in the peripheral auditory system and then changes the structure and function of the developing brain that is highly plastic, leading to neurodevelopmental deficits. Preterm babies in the neonatal intensive care unit often have various perinatal complications and/or major conditions that may directly or indirectly impair the central nervous system (CNS), including the central auditory system. Therefore, these babies may be at high risk of central auditory impairment, although this remains to be determined. Research suggests that central auditory impairment in children born with perinatal problems occurs more frequently than commonly recognized (3,4). However, detection of the impairment in infants is difficult.There are numerous reports on auditory impairment in preterm babies or children born preterm (5,6). These reports generally concentrated on peripheral auditory impairment and showed that peripheral impairment, including conductive and sensory or sensorineural, is a common abnormality present in preterm babies. On the other hand, there are very few reports on central auditory impairment.As an objective test to study functional integrity of the auditory brainstem, the BAER has been used to study functional development of the human auditory syste...