[영문]OBJECTIVES: We examined the effectiveness of a program to increase exposure to national qqqquot;truthqqqquot; tobacco countermarketing messages among youths in rural and low-population-density communities. METHODS: A longitudinal survey of 2618 youths aged 12 to 17 years was conducted over 5 months in 8 media markets receiving supplemental advertising and 8 comparison markets receiving less than the national average of qqqquot;truthqqqquot; messages. RESULTS: Confirmed awareness of qqqquot;truthqqqquot; increased from 40% to 71% among youths in treatment markets while remaining stable in comparison markets. Over 35% of all youths who were unaware of the campaign at baseline became aware of it as a direct result of the increased advertising. Youths living in rural and low-population-density communities were receptive to the campaign's messages. CONCLUSIONS: Through purchase of airtime in local broadcast media, the reach of a national tobacco countermarketing campaign was expanded among youths living in rural and low-population-density areas. This strategy of augmenting delivery of nationally broadcast antitobacco ads can serve as a model for leveraging limited tobacco control resources to increase the impact of evidence-based tobacco prevention campaigns.