Brainstem auditory function in small-for-gestational age (SGA) babies born at 30 and less weeks of gestation is poorly understood. We recorded and analysed brainstem auditory evoked response (BAER) at term in babies born at 26-30 weeks of gestation with a birthweight <3rd centile. Compared with normal term appropriate-for-gestational age (AGA) babies, the preterm SGA babies showed a significant increase in all BAER wave latencies at all click rates of 21-91/s (p < 0.05-0.001). The I-V and III-V interpeak intervals were also increased (p < 0.01-0.001), while the I-III interval was marginally decreased at 91/s (p < 0.05). No significant abnormalities were seen in wave amplitudes. Compared with age-matched preterm AGA babies, the SGA preterm babies showed an increase in wave I latency and a decrease in I-III interval at 51 and 91/s (all p < 0.05). No major and consistent differences were found in the two groups of babies in BAER wave amplitude variables. The increased I-V interval in the preterm SGA babies was correlated inversely with occipito-frontal head circumference at time of testing. CONCLUSIONS Brainstem auditory function is deviant from the normal in SGA babies born at 30 and less weeks of gestation. There is delayed brainstem neural maturation, which is associated with a small head size, and slightly precocial maturation in the more peripheral brainstem auditory regions. BACKGROUND Intrauterine growth retardation has a subtle degree of adverse effect on central brainstem auditory pathway in preterm babies born at 31-36 weeks of gestation. BACKGROUND Brainstem neural maturation is delayed, with slightly precocial maturation in the more peripheral brainstem auditory regions, in SGA babies born at 30 and less weeks of gestation.