Exciting advances in basic and clinical science brought a new strategy for antiretroviral therapy and new hope to people living with HIV in 1996. There are now three major categories of antiretroviral agents available for clinical use. All require replicating virus, and none are virucidal. The goal of antiretroviral therapy is a significant and prolonged reduction of the amount of actively replicating HIV (viral load). Carefully chosen combinations of antiretroviral drugs significantly reduce HIV load and are likely to extend life. However, not all patients respond to highly active antiretroviral therapy (HAART), and, for those who do, adjustment to demanding regimens and management of side effects may be difficult. The development of drug resistance is a serious concern, because resistance is associated with rising viral loads and with poorer prognosis in advanced disease.