This study examined how aggregate levels of news coverage about marijuana have impacted adolescents' marijuana behavior generally, and through the intervening variables of personal disapproval and perceived harmfulness of marijuana, two variables that existing research has identified as significant predictors of adolescent marijuana use at the aggregate level. It was hypothesized that news coverage of reasons why people should not use marijuana would cause increase in aggregate marijuana abstinence, perceived harmfulness, and personal disapproval. Conversely, news coverage of positive aspects of marijuana use would cause decreases in marijuana abstinence, perceived harmfulness, and personal disapproval. Results of distributed lagged time-series regression and non-linear modeling offered support for two of the three proposed hypotheses. Aggregate media coverage explained a significant portion of the variation in adolescents' abstinence from marijuana use over time. It also explained a significant portion of the variation in personal disapproval of marijuana. Personal disapproval was found to partially mediate the relationship between media coverage and marijuana abstinence. Implications for the conceptualization of media effects on health behaviors are discussed.