The authors evaluated the effect of a brief tailored smoking control intervention delivered during basic military training on tobacco use in a population of military personnel (N = 33,215). Participants were randomized to either a tobacco use intervention (smoking cessation, smokeless tobacco use cessation, or prevention depending on tobacco use history) or a health education control condition. Results indicated that smokers who received intervention were 1.16 (95% confidence interval [CI] = 1.04, 1.30) times (7-day point prevalence) and 1.23 (95% CI = 1.07, 1.41) times (continuous abstinence) more likely to be abstinent than controls from smoking cigarettes at the 1-year follow-up (p less than 0.01); the cessation rate difference was 1.60% (31.09% vs. 29.49%) and 1.73% (15.47% vs. 13.74%) for point prevalence and continuous abstinence, respectively. Additionally, smokeless tobacco users were 1.33 (95% CI = 1.08, 1.63) times more likely than controls (p less than 0.01) continuously abstinent at follow-up, an overall cessation rate difference of 5.44% (33.72% vs. 28.28%). The smoking prevention program had no impact on smoking initiation. These results suggest potential for large-scale tobacco control efforts.