OBJECTIVES: We examined the impact of a statewide antismoking media campaign on progression to established smoking among Massachusetts adolescents. METHODS: We conducted a 4-year longitudinal survey of 592 Massachusetts youths, aged 12 to 15 years at baseline in 1993. We examined the effect of baseline exposure to television, radio, and outdoor antismoking advertisements on progression to established smoking (defined as having smoked 100 or more cigarettes), using multiple logistic regression and controlling for age; sex; race; baseline smoking status; smoking by parents, friends, and siblings; television viewing; and exposure to antismoking messages not related to the media campaign. RESULTS: Among younger adolescents (aged 12 to 13 years at baseline), those reporting baseline exposure to television antismoking advertisements were significantly less likely to progress to established smoking (odds ratio = 0.49, 95% confidence interval = 0.26, 0.93). Exposure to television antismoking advertisements had no effect on progression to established smoking among older adolescents (aged 14 to 15 years at baseline), and there were no effects of exposure to radio or outdoor advertisements. CONCLUSIONS: These results suggest that the television component of the Massachusetts antismoking media campaign may have reduced the rate of progression to established smoking among young adolescents.