This paper presents the issues and main principles of community psychology and community research as well as associated relationships and viewpoints in terms of health psychology and social psychology. In this perspective, the paper presents the context in which community psychology has emerged and its fundamental principles such as empowerment, community involvement and the ecological model. Using two examples of research in prevention of HIV infection, the paper leads to a greater comprehension of how a particular community-based approach to involve affected populations may be particularly relevant, not only to better understand their beliefs and behaviors but also to try to encourage them to change current behaviors or generate new ones. Research with adolescents involved in promoting condom use illustrates the use of psychosocial models of behavior change through a community approach. A second research focus on medical and psychosocial innovation through the use of non-routine, rapid screening tests for HIV - which are neither carried out nor supervised by medical personnel - aims to highlight the impact of the development of preventive action by directly concerned communities. The article aims to present the innovative methodological and epistemological issues which underpin community research.