Twenty paid healthy students volunteered for a doubleblind cross-over trial on the effects of two weeks' treatment with placebo, thioridazine and bromazepam on psychomotor skills. The doses used were thioridazine 10 mg t.i.d. during the first week and 20 mg t.i.d. during the second week, or 6 mg of bromazepam t.i.d. during two weeks choice reaction test, two co-ordination tests, a divided attention test, flicker fusion, and proprioception tests were used. The psychomotor skills were measured in the afternoon of the 7th and 14th day of each treatment, 30, 90 and 150 minutes after the second daily administration of the drug in combination with either an alcoholic or a placebo drink. There were no significant differences between the test weeks. Thioridazine alone resembled placebo and had no major combined effect with alcohol. Bromazepam impaired reactive and co-ordinative skills and attention deteriorated. The combination of bromazepam and alcohol potentiated the deterious effects of the single agents, and this effect was most remarkable at 30 minutes. The subjects also gave exaggerated responses in the proprioceptive tests. No significant alterations were recorded in the flicker fusion frequency after any treatment.