Studies have shown that expectations of alcohol-induced impairment can produce adaptive responses to alcohol that reduce the degree of behavioral impairment displayed. The present study tested psychomotor performance following combined caffeine and alcohol administration in 42 social drinkers (23 men). Subjects were led to expect either that caffeine would antagonize alcohol-induced impairment or that it would have no effect. The study tested the hypothesis that drinkers who expected an antagonist effect of caffeine would display greater alcohol impairment than those who expected no antagonist effect.