A Study to Compare Three Doses of T-20 When Given in Combination With Abacavir, Amprenavir, Ritonavir, and Efavirenz to HIV-Infected Adults

Inclusion Criteria Patients may be eligible for this study if they: Are HIV-positive. Have an HIV level (viral load) between 400 and 100,000 copies/ml at the screening visit. Have taken at least 1 PI (protease inhibitor) for at least 16 weeks, and have had no interruptions in their most recent PI-containing anti-HIV drug regimen. Are at least 18 years old. Agree to abstinence or use of 2 effective methods of birth control, including a barrier method, during the study. Exclusion Criteria Patients will not be eligible for this study if they: Have ever taken an NNRTI (nonnucleoside reverse transcriptase inhibitor). Have an opportunistic (HIV-related) infection. Have had an unexplained fever of at least 38.5 C for 7 days in a row within 30 days prior to screening. Have had diarrhea lasting at least 15 days within 30 days prior to screening. Have ever taken abacavir, amprenavir, or efavirenz (ABC, APV, or EFV). Have certain genetic characteristics (drug resistance mutations) that could change the way a drug acts in the body. Are allergic to any of the study medications. Have a tumor other than certain skin or cervical cancers. Are on chemotherapy that cannot be discontinued during the study. Are taking an investigational drug within 30 days prior to screening. Have ever received an HIV vaccine. Are taking certain medications. Abuse drugs or alcohol. Have hemophilia or another blood clotting disorder. Have had an organ transplant. Are pregnant or breast-feeding.