Patients are seen in the clinic at pre-entry, baseline (Day 1), and every 4 weeks thereafter. Data on current antiretroviral treatment, HIV-1 associated conditions and adverse events are collected at every scheduled visit. Laboratory values (i.e., hematology, serum chemistry, plasma HIV-1 viral load and CD4+ cell count) are collected and assessed at pre-entry and Weeks 12, 24, 36, and 48. Optimal therapeutic effectiveness dictates the combined use of 2 or more antiretroviral agents in patients failing current antiretroviral therapy. APV, therefore, must be initiated as a component of a treatment regimen that also includes at least one other antiretroviral drug that the patient has not previously received.