Television has replaced the newspaper as the major source of news for most people, and thus has the potential to inform the public and influence attitudes. A growing literature has demonstrated the immediate effects of television viewing, but the ability of a particular program to have lasting effects is less clear. In this article, we report on two field experiments that provide a test of the durability of media effects by examining whether two television broadcasts had a lasting influence on viewers' knowledge and attitudes. Both television programs were designed to raise awareness about particular policy issues and to persuade. We find that one of the television programs affected viewer attitudes, even weeks after it aired, while the second television program did not. We consider why particular types of television programs and particular formats are better able to have a lasting impact on the public. Our findings suggest that message repetition is a crucial mechanism for influencing attitudes over the long-term.