ABSTRACT. Objective: This study examined how perceived risk for alcoholism and alcohol use infl uenced each other over time. We hypothesized an aversive transmission mechanism, by which some children of alcoholics may reduce their drinking because they perceive themselves to be at risk for future alcohol problems because of their parents' alcoholism. Method: Using participants (N = 804, 47% female) from an ongoing longitudinal study of children of alcoholics (e.g., Chassin et al., 1991), we examined the reciprocal prospective relations between perceived risk for alcoholism and drinking across three measurement occasions, and also tested whether perceived risk for alcoholism mediated the effect of perceived parental alcoholism on subsequent drinking. Results: Mediation analyses provided evidence for aversive transmission, in which the effect of perceived parental alcoholism on alcohol use during young adulthood was decreased to the extent that perceived parental alcoholism predicted higher levels of perceived risk for alcoholism during emerging adulthood. Results indicated reciprocal effects between perceived risk for alcoholism and drinking over time, such that higher levels of perceived risk were associated with lower levels of drinking. Results were replicated using both self-report and collateral-report of alcohol use, and using both actual and perceived parental alcoholism. Conclusions: Young adults may avoid drinking when they perceive their parent(s) to be alcoholic, and consequently perceive themselves to be at elevated risk for alcoholism. Given that beliefs about risk for alcoholism are potentially modifi able, increasing self-perceived risk for alcoholism may be one feasible way to reduce the intergenerational transmission of alcohol disorders within families. (J. Stud. Alcohol Drugs, 71, 588-596, 2010)