BACKGROUND: Caudal anesthesia is considered a safe and reliable anesthetic technique for many pediatric surgical procedures. It is well known that extradural clonidine produces analgesia in adult. The purpose of this study is to assess its efficacy in children. METHODS: We randomized 45 pediatric patients aged under 10 years, weighted under 25 kg presented for lower abdominal surgery with duration of operation would be shorter than 2 hours, into three groups of 15 each. After sedation with the use of intravenous thiopental sodium, caudal anesthesia was performed with the use of 1 mL/kg of 0.25% bupivacaine. We allocated randomly the patients who received no additional medication in 0.25% bupivacaine (group I), with epinephrine 1/200,000 (group II), and with 1 mcg/kg of clonidine (group III). The degree of postoperative analgesia was evaluated using the Broadman ""Objective Pain/discomfort Scale"" (OPS) at hourly intervals for 24 hours. RESULTS: Duration of sleep in the recovery room was significantly longer in group III than in group I and group II, and statistical significant difference was found between the group I and group II. Duration of analgesia was significantly longer in group III than in group I and group II. Overall hourly OPS scores were lower in group III than in group I and group II. CONCLUSION: Duration of postoperative analgesia with caudal bupivacaine was increased by addition of 1 mcg/kg of clonidine.