A fear appeal campaign to decrease the spread of genital warts was conducted and evaluated. Theoretically guided by the Extended Parallel Process Model, this field study illustrated why fear appeal campaigns often appear to fail in public health arenas. Five hypotheses, which predicted when and under what conditions fear appeal campaigns would fail or succeed, were tested and supported. The results demonstrated that fear appeals can be powerful persuasive devices if they induce strong perceptions of threat and fear (which motivate action) and if they induce strong perceptions of efficacy with regard to a recommended response (which channels the action in a health protective direction). Recommendations to researchers and public health practitioners are offered.