unlike most other sedative drugs, 2 adrenoceptor agonists e.g (clonidine) are capable of producing both sedation and analgesia with little if any, respiratory change. The aim of this study was to evaluate the analgesic efficacy, the respiratory and the endocrine effects of epidural versus intravenous clonidine for postoperative pain. Forty adult patients ASA I and II of both sexes were scheduled for elective lower abdominal or lower extremity surgical procedures. For postoperative pain relief , the patients were randomly divided into two groups, twenty patient of each. In (Group I) patients received intravenous clonidine through patient-controlled analgesia pump (IPCA). In (Group II) patients received epidural clonidine through patient-controlled analgesia pump (EPCA). A standard anaesthetic technique was employed to all patients and anaesthesia was maintained with gas oxygen halothane and muscle relaxant. Serial arterial and venous blood samples were taken to measure blood gases and endorphin level. After surgery patients with visual analogue scale ( VAS ) >4 were given clonidine initial dose 4µg/kg intravenous or epidural infusion over a period of 30 minutes then they were allowed to self administer clonidine using PCA pump which delivered a bolus dose of 0.5µg/kg with a 15 minute lockout interval to the corresponding route. Self-administered doses were (124.2±34.637µg) in intravenous group and (100.6±31.406µg) in epidural group. The total clonidine dose was (424. ±38.138µg) in intravenous group versus (399.8±47.371µg) in epidural group. Pain scores were lower after than before clonidine administration in both groups . No significant difference in pain scores were found between the two groups. There was also no significant changes in respiratory rate, arterial PH, Pa Co2 or Pa o2 in each studied group and no significant difference between the two groups. Forced vital capacity ( FVC ) and Forced expiratory volume in one second ( FEV1 ) were significantly reduced before clonidine injection in both groups. The beta endorphin level was increased after one hour of clonidine administration and there was no significant difference between the two groups. In conclusion Clonidine proves to be adequate alternative to opiates without their side effects and the dose of clonidine is lower by the epidural route.