Ambiguous biochemical and subjective responses to alcohol may relate to preexisting individual differences in alcohol expectations, experience, or impulsivity. This study examined cortisol and alpha-amylase responses to alcohol and their association with trait impulsivity, alcohol expectancy, and subjective reports of alcohol's effects. Eighty-seven males assigned to an alcohol, sober, or placebo group provided biochemical and self-report measures. Both cortisol and alpha-amylase increased following alcohol administration. Impulsivity correlated with cortisol changes, and the greatest rise in cortisol correlated with high stimulating effects in the alcohol group. These findings emphasize the importance of individual differences in alcohol responses and support a relationship between hormonal responses and alcohol use.