BACKGROUND: Epidural anesthesia (EA) has become most popular for cesarean section, but has some drawbacks such as incomplete block, inadequate muscle relaxation and delayed onset. Combined spinal epidural anesthesia (CSEA) has gained an increasing interest as it combines a reliability of the spinal block and the flexibility of an epidural block. We investigated the efficacy of CSEA which combines main spinal and supporting epidural anesthesia, comparing with pH adjusted EA, for cesarean section. METHODS: Sixty four pregnant women at full term were divided into two groups. Group 1 (n=32) received CSEA with 1.5~1.6 ml of 0.5% hyperbaric bupivacaine intrathecally, followed 10 minutes after by 10 ml of 0.25% plain bupivacaine through the epidural catheter. Group 2 (n=32) received EA with 20~25 ml of 2% lidocaine which was added 0.1 ml of 0.1% epinephrine, 100 microgram of fentanyl and 1.5 ml of 8.4% sodium bicarbonate. The quality and side effects of surgical anesthesia, neonatal state and postoperative course were compared between two groups. RESULTS: While 22% (7 cases) of Group 2 complained of intraoperative pain but none of Group 1 did (p=0.011). Muscle relaxation and motor block were much better in group 1 (p<0.001 and p=0.011 each). Significantly more women in group 2 had shivering (p=0.001) and they also had nausea and vomiting more, though that difference is not significant. Not only time to T4 (9.7 vs. 8.3 min., mean, p<0.001), but also stay at PACU, recovery of sensory and motor block and start of postoperative pain were all significantly shorter in Group 1. None of both groups had post-dural puncture headache (PDPH). CONCLUSIONS: We can conclude that CSEA, when combining main spinal and supporting epidural anesthesia, has greater efficacy and less side effects for cesarean section than pH adjusted EA.