An accordance with the clinical examination recommended by Lanz and Theiss, we studied 26 patients undergoing a blockade of the axillary plexus with lidocaine-CO2 or lidocaine-HCl. Furthermore, we determined the blood concentrations of these local anaesthetics. The study showed no significant differences between the two groups of patients, except that the onset of the blockade was more reliable in one group. There was less impairment of motor function than sensory function. Blood lidocaine concentrations amounted to 2.46 mg/l (mean value) within 25 min. Slight cerebral intoxication could be seen in four patients, with no correlation with possibly high lidocaine concentrations. Lidocaine CO2 is recommended as a rapid blockade of short duration in outpatient regional anesthesia.