Patients are stratified by antiretroviral experience: naive (no more than 2 weeks of therapy) versus experienced (more than 2 weeks). Patients must discontinue all antiretroviral therapy for at least 28 days prior to randomization to 1 of 9 HU treatment arms. Treatment arms are divided into 3 HU dose categories: very low, low, and medium. Within each category HU is administered daily on 3 different dosing schedules. Depending on viral load, patients on the very low and low dose arms may have the opportunity to intensify their HU dose at any time beyond Week 12, provided no Grade 3 or 4 HU-related toxicity is present (these patients are monitored for an additional 8 weeks following intensification). All patients receive ddI and d4T at the same doses every day. When 50% of patients have completed 24 weeks of treatment, an analysis is made to determine whether or not to continue the 52-week study without modifications. Patients are monitored periodically for changes in plasma HIV RNA, CD4 cell counts, weight, and symptoms.