The purpose of this study is to compare the safety and effectiveness of 2 dosing schedules (once daily vs twice daily) of lamivudine (3TC) given with stavudine (d4T) and either indinavir (IDV) or nelfinavir (NFV) for 24 weeks.

Patients are randomized to 1 of 2 groups. Group 1 receives 3TC qd plus d4T plus either IDV or NFV. Group 2 receives 3TC bid plus d4T plus either IDV or NFV. Patients are evaluated for drug tolerance, medication adherence, and genotypic and phenotypic resistance.

Inclusion Criteria

Patients may be eligible for this study if they:

• Are HIV-positive.
• Are at least 18 years old.
• Have had an HIV level below 400 copies/ml for at least 3 months prior to study entry.
• Have a CD4 cell count of at least 50 cells/mm3.
• Are currently taking an anti-HIV drug regimen that includes 3TC plus d4T plus either IDV or NFV for at least 6 months prior to study entry. (Note: This must be their first anti-HIV drug regimen.)
• Agree to abstain from sex or use effective methods of birth control during the study.

Exclusion Criteria

Patients will not be eligible for this study if they:

• Have a history of an AIDS-defining illness or certain other medical conditions.
• Are allergic to any of the study drugs.
• Are unable to take medication by mouth for any reason.
• Have received certain medications.
• Will need to receive radiation therapy or chemotherapy (for any cancer other than Kaposi's sarcoma) during the study.
• Are pregnant or breast-feeding.