The college environment appears to encourage heavy drinking. Consequently, correlates of student drinking were assessed at college entrance. First-semester freshmen (N = 520, 54 percent women) completed self-report measures of social affiliation and self/peer drinking for high school and college. Analyses indicated that: 1) increased drinking at college entrance mirrored perceived increases by peers, 2) perceptions of peer drinking were robustly overestimated with women displaying the larger overestimation bias; and 3) social affiliation was associated with men's drinking and moderated its relation to perceived peer drinking at college entrance. These results advance understanding of the manner in which heavy drinking patterns emerge as men and women enter college, and campus programs that consider these factors may better promote health and reduce the harms associated with heavy drinking among college students.