Forty-eight moderate social drinkers were assigned to one of four treatments: alprazolam (1 mg) and alcohol (0.5 g/kg); alprazolam (1 mg) and placebo drink; placebo capsule and alcohol (0.5 g/kg); and placebo capsule and placebo drink. Breath alcohol concentrations and ratings of mood and intoxication were completed at 90, 150 and 210 minutes post-drug (45, 105 and 165 minutes post-alcohol). Subjects competed in a competitive reaction time task at 105 minutes post-drug during which psychophysiological measures were simultaneously monitored. Active treatments increased sedation and intoxication and the task increased feelings of hostility and anxiety in all subjects. Aggressive responding increased in all groups in response to provocation but some stress response dampening was shown after both alcohol and alprazolam on the psychophysiological measures and after alprazolam on subjective ratings of anxiety. The combination of alprazolam and alcohol increased behavioral aggression more than would have been predicted from the sum of the single effects, confirming clinical reports of behavioral dyscontrol.