The growing population of Mexican American youth and the increasing smoking rates in this population present a considerable public health challenge. Tobacco counteradvertisements have demonstrated their ability to shape attitudes, behavior, and public policy, but little is known about the most effective ways to adapt messages aimed at this audience. To explore key variables that can affect success, a study was conducted with 249 Mexican American middle-school youth from a U.S./Mexico border community to examine the effectiveness of language (English, Spanish, or a combination of English and Spanish) and theme (secondhand smoke, antitobacco social norms, and tobacco industry manipulation) in print tobacco counteradvertisements. Measures included ad preferences, acculturation, and tobacco-related attitudes and behavior. Results showed that although a large percentage identified with the Mexican American rather than the Anglo American culture and spoke Spanish in selected contexts, readability was greater for ads in English, and participants rated the English ads as most effective. The social norms counteradvertisement was preferred overall. Potential implications for health communication and policy are discussed.