Objective: To determine which antitobacco messages were perceived effective in changing college students' knowledge, attitudes, and beliefs about tobacco use. Participants: College students (n = 1,020) were surveyed before and after viewing 4 30-second antitobacco advertisements in 1 of 3 theme categories--social norms, health consequences, or tobacco industry manipulation. Methods: An independent samples t test was used to test for differences in the mean responses to the knowledge, attitude, and belief questions at posttest by smoking status and gender. Results: Health consequences ads significantly increased overall knowledge and negative attitudes and beliefs. Conclusion: Findings from this study may help health educators who work in college settings and other young adult settings to include media messages as part of a comprehensive tobacco control program. (Contains 2 tables and 1 figure.)