A wide knowledge/behavior gap for avoidance and mitigation of HIV/AIDS infection throughout sub-Saharan Africa has persisted over the 30 years of the pandemic. Despite a relatively strong and rather widely distributed knowledge of the social biology of the disease, that knowledge has generally not been sufficiently internalized to induce major changes in sexual behavior of those most at risk. DHS data for Uganda, Kenya, and Tanzania are used to identify differentials in prevalence by gender, location, and education. Cultural practices affecting sexual behavior and exposure to infection, such as male circumcision and sexual cleansing, continue to be highly variable and are important determinants of the knowledge/behavior gap. Sexual behaviors remain filtered by culture to the extent that effective national HIV/AIDS policies cannot be driven only by national public information programs but need cultural sensitivity as well.