The pain threshold and pain tolerance were determined by electrical stimulation of the skin employing a newly-developed apparatus. The efficacy of the method was evaluated in a double-blind cross-over study on ten healthy subjects with administration of 50 mg pentazocine plus 500 mg acetylsalicylic acid (P + A) orally in comparison with a placebo. The sensitivity of this method in determining the pain threshold was compared with a fixed intensity-variable time modification of the radiant heat method. The presence of sedative side effects of the drugs was tested by measurement of the reaction time to visual stimuli. All measurements were performed before and then 60 and 90 minutes after drug administration and an analysis of variance was carried out on the data. There was a significant elevation of both the pain threshold and pain tolerance as determined electrically after the administration of P + A as compared with the placebo experiments. A similar tendency was obtained with the thermal method, but the increase in pain threshold was not statistically significant. No significant changes were found in optical reaction time. It may be concluded that the apparatus developed by us appears to be a valuable tool in the evaluation of effectiveness of analgesic drugs.