Social drinker volunteers were randomly assigned to the four cells of a balanced placebo design, with 10 males and 10 females per cell. They consumed a beverage which contained either tonic water only, or tonic water plus sufficient vodka to induce peak blood alcohol levels of approximately 0.05%. Subjects then completed a computer version of the Wisconsin Card Sorting Test (WCST) in two runs. Compared to tonic only, beverage alcohol selectively increased per cent perseverative errors as well as other measures of perseveration and the number of trials, p less than 0.05. Results are interpreted in terms of an hypothesized differential action on functions of the frontal cortex in addition to possible non-specific effects of alcohol. Issues pertaining to expectancy interpretations are also discussed.