BACKGROUND: During general anesthesia for a cesarean section, light depth of anesthesia frequently leads to maternal awareness and pain responses. The aim of this study was to evaluate the effects of alfentanil on the mother and neonate during a cesarean section. METHODS: Forty four parturients undergoing general anesthesia for an elective cesarean section were enrolled in this study. General anesthesia was induced with propofol 2 mg/kg and succinylcholine 1.5 mg/kg after an intravenous injection of normal saline 0.02 ml/kg for the control group or alfentanil 10microgram/kg for the alfentanil group. After tracheal intubation, anesthesia was maintained with O2 (2 L/min)-N2O (2 L/min)-isoflurane (0.5% end tidal). Mean blood pressure (MBP), heart rate, bispectral index (BIS) and maternal pain responses by an isolated forearm technique were measured every 1 min until delivery. Apgar scores of neonates were measured at 1 min and 5 min after delivery. RESULTS: There were no differences between groups in the MBP, BIS or maternal pain responses. However heart rates were lower in the alfentanil group than in the control group (P = 0.017). CONCLUSIONS: The supplemental administration of alfentanil 10microgram/kg can attenuate the changes in maternal heart rate during general anesthesia for a cesarean section without neonatal Apgar score decline.