Individual, household and community-level influences on young people's (15-24) knowledge of HIV/AIDS in three African countries (Burkina Faso, Ghana and Zambia) are explored. The focus of the analysis is on the roles of demographic, economic and behavioral dimensions of the community environment in shaping knowledge of HIV/AIDS. Data from Demographic and Health Surveys, collected independently for males and females in each of the countries, are analyzed. There are clear pathways through which the community environment shapes knowledge, and the community influences on knowledge vary greatly by country and gender. For young women, residences in communities with demographic and behavioral patterns that are indicative of greater opportunities are associated with increased knowledge of HIV/AIDS. The results highlight community-level factors that can be harnessed in the development of community-based interventions to improve knowledge of HIV/AIDS among young people, and reinforce the need to focus on the community environment in designing behavioral change interventions.