This study examined HIV risk behaviors among 5,059 adults over age 40 in South Africa, using data from the Health and Aging in Africa: Longitudinal Studies of INDEPTH Communities (HAALSI) study. The study showed an HIV prevalence of 23 percent, with no differences by sex. Participants reported multiple sexual risk behaviors; 67 percent reported having multiple sexual partners in their lifetime, and 57 percent had at least one sexual partner in the last two years. Three-quarters of recently sexually active participants reported never using condoms with their most recent partner. Men reported sexual activity at higher rates than women at older ages (52% versus 17% at age 80). HIV-positive individuals who knew their status were most likely to use condoms, followed by HIV-positive individuals unaware of their status, and then by HIV-negative individuals. Twelve percent of participants reported having had casual sex; HIV-negative individuals were least likely to do so (9%), compared to HIV-positive participants who were aware of their status (29%) and those who were unaware (18%). HIV-negative individuals were least likely to report multiple partners (8%); 9 percent of HIV-positive unaware individuals and 13 percent of status-aware individuals reported multiple partners. The authors concluded that adults over age 40 face significant HIV acquisition risk and require targeted prevention interventions.