Peripheral administration of opioids has been suggested as a means of improving regional block. We studied 60 patients receiving axillary brachial plexus anaesthesia, allocated randomly to receive either normal saline 10 ml or normal saline 10 ml with alfentanil 10 micrograms/kg body weight through an axillary cannula. All patients received 1.5% lignocaine at a dose of 7 mg/kg body weight with adrenaline 1 in 200,000. The incidence of satisfactory block was similar in both groups. Although the percentage of patients with complete anaesthesia in the median nerve distribution was greater in the alfentanil group, there was no significant difference in any other distribution. The time to return of sensation and motor function was prolonged significantly in the alfentanil group (P < 0.05). After return of normal sensation, there was no significant difference between groups in postoperative analgesia. In a second part of the study, there was no significant increase in plasma concentrations of alfentanil in 10 patients given lignocaine and alfentanil, as outlined above. These observations suggest that alfentanil may have a peripheral local anaesthetic action.