The immunomodulatory capacity of acute, moderate alcohol consumption was investigated in this study in nonalcoholic volunteers after 2 ml of vodka/kg body weight of alcohol consumption. There was a significant, transient increase in interleukin-12 and interferon-gamma (IFNgamma) levels in whole blood samples collected 4 hr after alcohol consumption in response to an ex vivo bacterial challenge with lipopolysaccharide (p < 0.02). However, decreased IFNgamma levels were produced by mononuclear cells collected later after alcohol consumption (16 hr), suggesting that acute alcohol consumption has a biphasic effect on IFNgamma inducibility. Furthermore, isolated blood monocytes collected 16 hr after alcohol consumption showed significantly decreased IL-1beta production in response to subsequent bacterial stimulation, implying that in vivo alcohol consumption affects monocyte-derived inflammatory cytokine production. These results demonstrate that even acute, moderate alcohol consumption has a modulating capacity on immune functions that may contribute to decreased immunity and host defense.