The authors combined the 2-step flow of communication model and the theory of planned behavior to create a framework to evaluate the effectiveness of a set of advertisements from the National Youth Anti-Drug Media Campaign promoting parent-child drug communication. The sample consisted of 1,349 pairs of parents and children who responded to the first and second annual rounds of the National Survey of Parents and Youth, and 1,276 pairs from Rounds 3 and 4. Parents' exposure to the campaign reported at Round 1 was indirectly associated with youth's lowered intentions to use marijuana at Round 2. Ad exposure was associated with positive changes in parental attitudes toward drug communication and perceived social approval of antidrug communications. These two beliefs, along with perceived behavioral control, predicted parents' intentions to discuss drugs with their children. Parental intentions to discuss drugs reported at Round 1 were associated with youth's report of actual drug communication with their parents at Round 2. Frequency and breadth of the topics in parent-child drug communication were associated with less positive attitudes toward marijuana use among youth who spoke with their parents. Together, the child's attitudes toward marijuana use and perceived ability to refuse marijuana use predicted youth's intentions to use marijuana. The proposed model fit well with the data and was replicated in a parallel analysis of the data from Rounds 3 and 4. Implications for future antidrug media campaign efforts are discussed.