The study is a 7-session, double blind, placebo-controlled crossover study of the effects of tolcapone, the COMT inhibitor, on decision making and alcohol intake using a laboratory bar in moderate to heavy social alcohol drinkers. Subjects will be moderate to heavy social users of alcohol, defined as at least 10 standard drinks per week for women and at least 14 standard drinks per week for men. There will be one screening session followed by six additional visits including 2 laboratory bar sessions. On each study drug administration day, subjects will come in to the clinic for a medication dispensation visit and instructions on when and how to take the study drug for the remainder of the study. Study drug bottles will be equipped with MEMS caps to ensure compliance. After 5 days of drug administration, subjects will return to the clinic for a laboratory bar. This session will consist of administration of a standardized laboratory bar paradigm and a series of computerized and written decision-making tasks. Subjects will then be crossed over and complete the same series of study visits on the alternate study drug.