BACKGROUND: When clonidine is mixed with local anesthetics, it extends the duration of both the motor and sensory elements of spinal, epidural, axillary, peripheral nerve block. This study was designed to determine whether the addition of clonidine to 1% lidocaine would produce significant extension of anesthetic and analgesic effect after axillary brachial plexus block and to assess the incidence and severity of side effect. METHOD: Sixty patients who were scheduled for hand surgery received 1% lidocaine 40 ml (Group L), 1% lidocaine 40 ml with clonidine 75 microgram (Group C75) or 150 microgram (Group C150) during axillary plexus block. Time from the performance of the block to 1) loss of pain sensation to pinprick, 2) return of pain sensation to pinprick, 3) onset of postsurgical pain and 4) time of first analgesic medication were recorded. Blood pressure, heart rate and sedation and pain score were checked every 10 min after block. RESULTS: The onset time of anesthesia in Group C75 and Group C150 were shorter than that of Group L (p<0.05). The duration of anesthesia and analgesia and the time to first analgesics medication in Group C75 and Group C150 were longer than that of Group L (p<0.05). Group C75 and Group C150 represented higher sedation score than Group L (p<0.05). CONCLUSION: The addition of clonidine (75 microgram or 150 microgram) to 1% lidocaine significantly prolongs the duration of anesthesia and analgesia after brachial plexus block and induces some degree of sedation without significant side effects.