Twenty male volunteers, average age 23, were studied in the fasting state at a week interval in the morning between nine and ten a.m. A brachial blood pressure cuff was inflated to a pressure of 250 mmHg and the subject squeezed a hand dynamometer to half of maximum strength for two ten seconds periods. The subject then started to report his sensory experience every ten seconds for 15 minutes by pointing at a scale consisting of six categories from "nothing" to "extremely painful". The first trial was performed on all unmedicated subjects, the non dominating arm was used. The second trial was performed on the opposite arm, 45 minutes after oral double-blind randomized administration of a capsule containing either 1 g aspirin or 300 mg tiapride. The answers of the subjects were statistically analysed using paired comparisons tests. Results indicate that tiapride exerts a significant antalgic effect from the 6th minute to the end of the experiment when compared to the control (p less than 0.05 to p less than 0.01). Aspirin produces a similar antalgic effect which occurs earlier, after 4 minutes. The mechanism of the antalgic effect of tiapride has been attributed to the release of beta-endorphine produced by benzamide which is associated with a decrease in plasma dopamine and a parallel increase in prolactine.