In an attempt to curb excessive drinking on college campuses, many universities have turned to "social norms" marketing campaigns. Despite widespread acceptance among health educators, empirical results are clouded by measurement problems. This study, based on a random sample of 550 students, examined the effects of misperceptions of friends' and typical college students' drinking on one's drinking behavior. Results indicate that drinking behavior is positively related to perceptions of friends' drinking as suggested by the theory of planned behavior, which emphasizes subjective as opposed to social norms.