The overall goal of the proposed research is the identification of physiologically-based factors associated with underage drinking. Of particular interest is the extent to which physiologically-based factors are related to subjective response to alcohol and whether or not they differentiate underage drinkers who maintain, transition into, or transition out of, heavy drinking patterns. As a replication and extension of preliminary findings, Study 1 will combine questionnaire and experimental methodologies in a sample of underage first-year college students to (a) provide a critical examination of the factor structure of self-report measures of perceived subjective response to alcohol, (b) identify physiologically based factors associated with heavy drinking patterns, and (c) determine whether these physiologically-based factors are associated with the experience of alcohol-related problems. By combining the methodology established in Study 1 with a standardized alcohol administration in a sample of 21 year-old participants, Study 2 will (a) evaluate the construct validity of self-report measures of perceived subjective intoxication, and (b) examine the association between physiologically-based factors related to heavy drinking patterns and subjective response to alcohol. Using participants recruited from an NIAAA-funded longitudinal project, Study 3 will identify physiologically-based factors that differentiate underage drinkers who maintain, transition into, or transition out of, heavy drinking patterns during the transition from high school to college. [unreadable] [unreadable]