Hingson and Howland (2002) estimated that 1,138 college students die from alcohol-related traffic crashes annually. An additional 307 college students die annually from alcohol-related non-traffic unintentional injuries and 500,000 college students annually sustain alcohol-related injuries (Hingson and Howland 2002). 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. If young people erroneously believe that caffeine in beer will protect them from alcohol-related injury, then such beverages may increase mortality and morbidity in this population. Thus, it is important to have accurate information about the extent to which such beverages affect impairment both acutely and residually. Such information could correct misunderstandings young people have about the relative safety of caffeinated beer and thereby reduce injury. The study could have implications for safety-sensitive occupations as well. It is common for people to use caffeine to counteract the sedative effects of alcohol. If, however, the alcohol and caffeine interact to yield greater impairment in next-day performance, workers should be aware of this, particularly if their jobs have low tolerance for error. This study, to our knowledge, will be the first to compare the acute and residual effects of caffeinated and non-caffeinated beer on driving performance. Objectives: The aim of this study is to develop information about the acute and residual effects of a new product being targeted to young adults. It is important to understand the effects of caffeinated alcoholic beverages early on in the marketing campaign so that if they pose a greater threat to pubic health than traditional alcoholic beverages, (1) consumers can be educated and (2) policy-making can be informed with accurate information. We will compare the acute and residual effects on driving impairment of caffeinated and non-caffeinated beer to each other and to placebo when participants have received sufficient alcoholic beverage to attain a blood alcohol concentration (BAC) of .12 g%. Study Design: We will conduct a placebo-controlled trial using a 2 X 2 mixed-model study design. The within-subjects factor will be alcohol vs. placebo; the between-subjects factor will be caffeinated vs. noncaffeinated beer. Setting: The study will take place at the General Clinical Research Center at Boston Medical Center. Participants: We will recruit 144 students from Boston area Universities. Outcome Measures: Acute and residual driving impairment will be assessed using a driving simulator and an objective measure of sustained attention/reaction time, the Psychomotor Vioilance Test (PVT).