Patients undergo genotypic analysis after registration to Step 1. Genotypic antiretroviral resistance test (GART) along with a patient's antiretroviral drug history will be used to select an optimal antiretroviral drug regimen (non-study drugs) for each patient. Patients willing to initiate the GART-based regimen are randomized at Week 5 into Step 2. They are stratified, first by level of ddI resistance, then within each strata by CD4+ T cell count, and then assigned to 1 of 3 treatment arms to start all study drugs (ddI and hydroxyurea) and non-study antiretroviral drugs on the day of randomization. Patients in Arm A receive ddI and hydroxyurea placebo; Arm B, ddI and hydroxyurea placebo that is replaced by hydroxyurea after 8 weeks; and Arm C, ddI and hydroxyurea. Patients receive treatment for 48 weeks. Patients are checked regularly for immunologic, virologic, and metabolic parameters. Patients may elect to participate in substudy A5070s, which explores the effects of study treatment on T cell populations and other immunologic evaluations.