Abstract This article examines the impact of HIV/AIDS on the armed forces and the implications high infection rates among military personnel poses for national and international security. Data are provided of the current HIV/AIDS infection rates in the different regions of the world, with specific reference to Southern Africa and the armed forces of the region. The implications high infection levels within African armed forces hold for operational effectiveness are highlighted and the impact this epidemic has on future peacekeeping and humanitarian aid missions discussed. In the last section of the article, the link between human, national and international security are expanded upon, emphasising the destabilising effect HIV/AIDS has on global security and why this disease has been declared one of the most pressing transnational security challenges facing mankind.