[Note: As of 2/28/2001, due to toxicity studies and concerns for safety, sites were notified that they need to discontinue patients from the capravirine/placebo arms and continue patients with their background therapies or switch patients to new therapies, as deemed appropriate by the investigators.] Patients are randomized to receive Viracept plus Combivir plus either AG1549 or placebo. Patients remain on their assigned therapy for 48 weeks with one post-therapy follow-up visit. Blood samples are taken regularly to quantify plasma HIV-1 RNA, CD4 and CD8 counts, and peripheral blood mononuclear cells (PBMC). Physical exams, safety assessments, and other tests are also done throughout the study. A blood sample is taken at baseline (pre-dose) for a pharmacokinetics assessment. On Day 8 and at the end of Weeks 4, 8, 16, 24, 36, and 48, pharmacokinetic sampling is done prior to dosing and between 2 to 4 hours post-dose.