objective: dengue has been endemic in puerto rico for three decades. multiple educational and community-based efforts have been developed to inform the population about dengue prevention. we undertook this study to understand the community members' knowledge, attitudes, and practices related to dengue prevention and to elicit their ideas for future prevention campaigns. methods: a qualitative study based on grounded theory analysis was conducted between february and may of 2001. the study involved a total of 34 participants in four group interviews who had been identified through the puerto rico dengue surveillance system. results: in general, participants had correct knowledge about dengue prevention, but they did not associate the mosquitoes inside their houses with aedes aegypti. participants insisted that "neighbors" needed to control larval habitats, and the participants also asked the government to fumigate. conclusions: the patterns of knowledge and opinion that emerged in the discussions can be arranged along an axis going from high levels of correct knowledge to low levels of correct knowledge about dengue and dengue hemorrhagic fever and related practices. there were few participants at either extreme. three themes explained these patterns: misconceptions about dengue (based on previously delivered information), the "invisibility" of dengue (as compared to other diseases), and responsibility (individual and government). four strategies for preventive behaviors were recommended: developing community groups to identify community priorities on prevention, developing volunteer groups to deliver prevention messages, making house visits to demonstrate specific control measures, and conducting a complementary media campaign to support these strategies.