Caffeinated alcoholic beverages target young adults with the promise that the caffeine will counteract the sedating effects of alcohol and thus let the consumer remain alert and active longer, while continuing to drink. It is likely that in the minds of some young people, this promise also translates into the idea that mixing caffeine with alcohol allows one to drive more safely than would be possible after having consumed an equivalent amount of non-caffeinated alcoholic beverage. These are dangerous assumptions because (1) alertness may not indicate the absence of impairment under intoxication and (2) next-day impairment from the residual effects of heavy drinking may be exacerbated by mixing caffeine and alcohol. We will compare the acute and residual effects of caffeinated and non-caffeinated beer in terms of a highly relevant outcome - the ability to drive safely.