Objective To investigate the efficacy of amplitude-integrated electroencephalographic (aEEG)in evaluating the maturation of cerebral function in preterm infants.Methods Ninety one neurologically normal and clinically stable preterm infants admitted to neonatal intensive care unit were studied prospectively by using aEEG.Background of aEEG activity patterns,presence of sleep-wake cycles,and the lower and higher border were analyzed.Results 112 aEEG were analyzed.The sleep-wake cycle and the continuity became more mature with PMA increased.The lower border were increased and the higher border were decreased with PMA increased(r =0.982,P ＜ 0.01 ; r =-0.964,P＜0.01).Conclusion In preterm infants,aEEG is a useful tool to evaluate the maturation of cerebral function.