A mixture of carbonated lignocaine and bupivacaine for axillary blocks was assessed prospectively in a randomized double-blind study including 60 patients scheduled for upper limb surgery. A peripheral nerve stimulator was used to carry out the axillary block with a multiple injection technique. The musculocutaneous, radial, median and ulnar nerves were routinely stimulated. Four criteria were monitored: quality of sensory blockade, degree of motor blockade, time of onset and duration of anaesthesia. The patients were randomly assigned to three groups (n = 20 each). Patients received 25 ml per m2 of body surface area of either carbonated 1% lignocaine (group 1) or 0.25% bupivacaine (group 2) or a 1 to 1 mixture of both (group 3). Adrenaline (1 in 400,000) was added to half the anaesthetic solutions used in each group. The onset of anaesthesia was faster with the mixture (15 +/- 9 min) than will bupivacaine alone (23 +/- 14 min) (p < 0.02). It lasted longer in the mixture group (264 +/- 111 min) than in the lignocaine group (193 +/- 83 min). The longest duration was in the bupivacaine group (476 +/- 276 min) (p < 0.03). Adrenaline only affected significantly the duration of anaesthesia in the lignocaine group (252 min vs 135 min with and without adrenaline, respectively) (p < 0.03). In axillary blocks, the mixture of carbonated lignocaine and bupivacaine has a faster onset of action than bupivacaine alone, and a longer duration of action than lignocaine alone. Both agents provided a quality of sensory and motor blockade similar to that obtained with the mixture.