[Note: As of 2/28/2001, due to toxicity studies and concern for safety, patients need to sign new informed consents. Patients who are taking capravirine and who currently have viral loads below 400 copies/ml may continue to take capravirine at 1400 mg twice daily. Capravirine will be discontinued in patients with viral loads greater than 400 copies/ml at their last visit and they will be switched to new therapies or continue with their background therapies as deemed appropriate by the investigators.] This study will take place in approximately 150 centers in the US, Canada, Europe, Australia, Argentina, and South Africa. Patients are randomized to 1 of 2 treatment groups and stratified by geographic sites (North American and non-North American), plasma HIV-1 RNA levels, and prior NNRTI use. Group 1 patients receive capravirine plus VIRACEPT plus 2 new NRTIs and Group 2 patients receive capravirine placebo plus VIRACEPT plus 2 new NRTIs. NRTIs will not be provided by the sponsor. Patients may remain on their assigned treatment for 48 weeks, with posttherapy follow-up occurring at 1 and 3 months. Assessments, done at various times throughout the study, include medical history, HIV antibody test, complete or symptom-directed physical examination, vital signs, height, weight, serum pregnancy test, hematology, chemistry, and recording of concomitant medications and adverse events. Other select assessments are performed at specified visits. Plasma samples for resistance testing and blood specimens for peripheral blood mononuclear cells (PBMC) are obtained at several times. The plasma samples and PBMCs may be used for viral drug resistance testing. Blood samples for quantitation of capravirine, VIRACEPT, and M8 (a metabolite of VIRACEPT) plasma concentrations are collected several times. Additional blood samples for analysis of drug concentrations may be requested depending on concomitant NRTIs or other medications. A Data Safety Monitoring Board monitors patient safety at prescribed intervals during the study.