Postoperative pain is still troublesome for patients. A prospective randomized study performed to determine morphine additive effect to local anesthetic for brachial plexus block should provide longer postoperative analgesia. Fifty Thai patients, 15-50 years old, were divided into 2 groups, 30 patients in group I received morphine hydrochloride 100 mg/kg and 1.5% lidocaine (with epinephrine 1: 200,000) 20 ml while 20 patients in group II received 1.5% lidocaine (with epinephrine 1 : 200,000) 20 ml and normal saline. The duration of postoperative analgesia was evaluated by using visual analogue scale at 0, 6, 12 and 24 hours postoperatively.In morphine group, analgesia extended over 12 hours about 66% while only 15% is in controlled group. The side effects were nausea/vomiting and sedation. Nausea/vomiting found in 11 patients (36.67%) was successfully treated with metoclopramide and sedation was found in 4 patients (13.33%) of morphine group. We conclude that adding morphine in the brachial plexus block will be a better postoperative analgesia for upper limb surgery.