We have investigated the local anaesthetic effects of 0.1% and 0.2% pethidine compared with 0.5% prilocaine using an intravenous regional anaesthetic technique, in a randomised, double-blind study in volunteers. Both pethidine and prilocaine produced a sensory and motor blockade, although the latter had a more profound effect, with a faster onset and slower recovery. Pethidine in low concentration clearly has a local anaesthetic action on peripheral nerves.