Four studies examined the relation between college students' own attitudes toward alcohol use and their estimates of the attitudes of their peers. All studies found widespread evidence of pluralistic ignorance: Students believed that they were more uncomfortable with campus alcohol practices than was the average student. Study 2 demonstrated this perceived self-other difference also with respect to one's friends. Study 3 traced attitudes toward drinking over the course of a semester and found gender differences in response to perceived deviance: Male students shifted their attitudes over time in the direction of what they mistakenly believed to be the norm, whereas female students showed no such attitude change. Study 4 found that students' perceived deviance correlated with various measures of campus alienation, even though that deviance was illusory. The implications of these results for general issues of norm estimation and responses to perceived deviance are discussed.