Perivascular axillary blockade was performed on 60 patients with the aid of a catheter technique. The patients were randomly allocated to two groups. All patients received the same dose of local anaesthetic: 60 ml of mepivacaine 1 % with adrenaline, but one group received the dose as a bolus injection, whereas the other group received the dose as fractional injections of 30 + 30 ml with an interval of 20 min. Blood concentrations of mepivacaine were measured up to 90 min after injection of local anaesthetic. Sensory and motor blockade were evaluated 20, 30 and 40 min after injection. Forty minutes after the last injection of local anaesthetic, there was no difference between the blockades of the two groups, except for the sensory blockade of the lower lateral cutaneous nerve of the arm, in which the frequency of analgesia was 90% after bolus injection and 63% after fractional injections. There was no difference in blood concentrations of mepivacaine between the two groups. None of the 60 patients showed any sign of systemic toxic reactions. Fractional injection of local anaesthetic in perivascular axillary blockade does not offer any advantage over bolus injection with regard to the resulting blockade.