We have studied 40 patients undergoing elective shoulder surgery for chronically painful conditions. Patients were allocated randomly to two groups and received interscalene brachial plexus block with 0.5% bupivacaine and adrenaline 1/200,000 40 ml either alone or with the addition of morphine 5 mg. All patients also received a general anaesthetic. The quality of the block, analgesic requirements and any complications or side effects were noted in the intraoperative period and during the 48 h after operation. No significant difference was seen in quality of analgesia or patient satisfaction between the two groups.