Objective: Previous research has shown that students overestimate the drinking of their peers, and that perceived norms are strongly associated with drinking behavior. Explanations for these findings have been based largely on cross-sectional data, precluding the ability to evaluate the stability of normative misperceptions or to disentangle the direction of influence between perceived norms and drinking. The present research was designed to evaluate (1) the stability of normative misperceptions and (2) temporal precedence of perceived norms and drinking. Method: Participants were college students (N = 164; 94 women) who completed assessments of perceived norms and reported behavior for drinking frequency and weekly quantity. Most participants (68%) completed the same measures again two months later. Results: Results indicated large and stable overestimations of peer drinking for frequency and weekly quantity. Results also showed that for weekly quantity, perceived norms predicted later drinking, but drinking also predicted later perceived norms. Results for frequency revealed perceived norms predicted later drinking, but drinking did not predict later perceived norms. Conclusions: These findings underscore the importance of longitudinal designs in evaluating normative influences on drinking. The present findings suggest that normative misperceptions are stable, at least over a relatively short time period. Findings support a mutual influence model of the relationship between perceived norms and drinking quantity but are more strongly associated with conformity explanations for the relationship between perceived norms and drinking frequency. Results are discussed in terms of implications for prevention interventions.