Eight male subjects took none or 200 mg fenmetozole 1 hr before drinking a beverage containing none or 50 ml/70 kg ethanol. Tests designed to measure mental and motor performance were administered 2 hr after fenmetozole ingestion. Fenmetozole alone impaired standing steadiness but improved mental performance in one test. Fenmetozole did not antagonize the decrement in performance induced by this amount of ethanol. In combination, the subjective symptoms caused by fenmetozole were additive with those of ethanol.