The caudal epidural anesthesia has been popular due to the postoperative pain relief and the reduction of the amount of general anesthetics. It is also technically simple and safe both for inpatients and outpatients under the age of 7 Year. The aim of this study was to determine the adequate dosage and degree of postoperative pain relief according to the different local anesthetics. We have performed the caudal anesthesia in 60 patients from the age of 10 month to 7 year. All caudal blocks were performed under light general anesthesia in order to relief the fear and anxiety of operation. The patients were divided by 4 groups of each 15 children. Group 1 (control group) for 1% lidocaine 1 ml/kg, Group 2 for 1% lidocaine 0.8 ml/kg, Group 3 for 0.25% bupivacaine 0.8 ml/kg, Group 4 for 0.25% bupivacaine 0.6 ml/kg. All groups were given 1:200,000 epinephrine. The overall success rate of caudal blocks was 98%. Complication was 3 cases. As the result of this study, Group 1 (control group): There was sensory block over T4 (20%). The degree of motor block was very high(73.3%). Group 2 and 3: There was no sensory block over T4. Duration of postoperative analgesia was long enough compared to the control group (p<0.05). The degree of motor block was less than the control group. Group 4: The height of most sensory block was below T8 (80%). The degree of motor block was very low (p<0.05) and duration of postoperative analgesia was short compared to the control group (p<0.001). Therefore it is considered that caudal blocks in Group 2 & 3 were adequate dosage for the pediatric operation.