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Background: The main advantage of regional anesthesia is the elimination of post-operative pain without the need for narcotics, which leads to a more rapid outpatient recovery and faster return to consciousness in pediatric patients. The aim of this study was to compare caudal anesthesia with midazolam and neostigmin co-administered with bupivacain in reduction of post-operative pain in lower abdominal surgery in pediatrics (2- 8 years old). Materials and Methods: In a double-blind clinical trial, 45 pediatric patients were randomly allocated to midazolam, neostigmine, and placebo groups. Induction of anesthesia was done with inhalation of halothane and O2. Bupivacaine 0.25% in 0.5 ml/kg with midazolam in 50μ/kg was administered in caudal form to the first group, and bupivacaine 0.25% in 0.5 ml/kg with neostigmine in 2 μg/kg dose was administered to the second group. The third group received the placebo plus bupivacaine 0.25% in 0.5 ml/kg. Results: Mean durations of analgesia in neostigmin, midazolam, and placebo groups were 16.5± 0.25, 12.3±0.22, and 6±0.11 hours, respectively (P<0.001). Also, in the neostigmin group, mean score of pain in outpatient recovery 6 , 12 , 24 hours post operatively was less than that in the other two groups (P<0.001). Conclusion: Duration of analgesia period in neostigmin group was more than that in midazolam and placebo groups