Cheap and widely available antiretroviral therapy for treating HIV and AIDS may seem like the solution to Africa's AIDS epidemic. But if not carefully planned and carried out, any programmes to administer the drugs could be disastrous. In this article, Warren Stevens, Steve Kaye and Tumani Corrah of the Medical Research Council Laboratories in Banjul, Gambia, argue that consistent prescription and close monitoring of the drugs are essential to prevent widespread drug resistance.