OBJECTIVES: This study evaluated the effectiveness of targeted televised public service announcement campaigns in reducing marijuana use among high-sensation-seeking adolescents. METHODS: The study used a controlled interrupted time-series design in 2 matched communities. Two televised antimarijuana campaigns were conducted in 1 county and 1 campaign in the comparison community. Personal interviews were conducted with 100 randomly selected teenagers monthly in each county for 32 months. RESULTS: All 3 campaigns reversed upward developmental trends in 30-day marijuana use among high-sensation seekers (P š .002). As expected, low-sensation seekers had low use levels, and no campaign effects were evident. CONCLUSIONS: Televised campaigns with high reach and frequency that use public service announcements designed for and targeted at high-sensation-seeking adolescents can significantly reduce substance use in this high-risk population.