The participants were students enrolled in a required introductory English class. The sample consisted of all enrolled students who were in attendance on the day the survey was administered. Estimations of the percentage who used marijuana exceeded the percentage of students who reported current marijuana use. Students estimated that 34.9 percent of male students and 27.7 percent of female students used marijuana in the past month. However, 29.6 percent of males and 19.6 percent of females reported use in the past month. Marijuana users gave significantly higher estimates of the percentage of users than did nonusers. The risk of using marijuana was also much greater among students who held the perception that more than half the students used marijuana and therefore that marijuana use was normative on campus. Marijuana users were also at significantly higher risk of other drug use and sexual activity. Female marijuana users were more likely to have an eating disorder and ever to have attempted suicide. Findings suggested the need to provide accurate information about the prevalence of marijuana use on college campus and to send the message that marijuana use is not normative on campuses. Prevention programs also should target marijuana users, because they are at high risk for engaging in risk-taking behaviors related to health. Tables and 26 references (Author abstract modified)