HIV disease is characterized by a progressive decline in CD4 cells and an increase in viral burden. Although antiretroviral therapy has been successful in controlling viral levels, its effects on CD4 cell counts have been modest. Intermittently administered IL-2 in the presence of HAART has been shown to increase CD4 cell counts, decrease lymphocyte activation markers, and increase certain lymphocyte functional activity in patients with early-stage HIV infection. ACTG 328 evaluated the effects of intravenous and/or subcutaneously administered IL-2 in conjunction with HAART in a group of more advanced HIV-infected patients over an 18- to 22-month period. As patients were enrolled in this study over an 18-month period, a follow-up protocol is required to provide continued IL-2 therapy for patients responding to IL-2 and patients in the control group who wish to receive this drug.