Background: Pain in infancy is a developmental process. Due to the underdeveloped pain pathways in the spinal cord, the threshold of stimulation and sensation of pain is low at birth and has potential impacts on increasing the central effects of pain. Primary trauma during infancy can cause long term changes in structure and function of pain pathways that continue until adulthood. Lack of pain management in children can result in morbidity and mortality. Objectives: In this study we examined the duration of post-operative analgesia in children when clonidine is added to bupivacaine in caudal anesthesia. Materials and Methods: In this clinical trial, 40 children aged 1-8 years who were candidates for elective inguinal hernia repair were studied. Induction and maintenance of anesthesia were achieved using sodium thiopenthal, halothane and nitrous oxide. Children were randomly divided into 2 groups in a double-blind fashion, and were given caudal anesthesia with 0.125% bupivacaine (1ml/kg) alone or b bupivacaine plus 2 µg/kg clonidine. Blood pressure and heart rate were recorded peri-operatively. Analgesia was evaluated using objective pain scale (OPS) and sedation was assessed using Ramsay sedation scale (RSS). Acetaminophen was administered rectally for cases with OPS score greater than five. Results: Duration of analgesia was found to be significantly longer in the group given bupivacaine plus clonidine (mean 417.50 min vs. 162.00 min). Peri-operative hypotension or bradycardia, post-operative respiratory depression, nausea or vomiting were not recorded in any patient. Conclusions: We concluded that addition of clonidine to bupivacaine prolongs the duration of post-operative analgesia without any respiratory or hemodynamic side-effects.