Patients are randomized to one of two arms in a 2:1 ratio (weighted to Arm 1). Arm 1: Replace lamivudine with FTC while continuing on current background regimen. Arm 2: Continue on current lamivudine-containing regimen. Patients are further stratified based upon screening plasma HIV-1 RNA and background therapy. Stratum 1: Less than 50 copies/ml; PI (protease inhibitor) in treatment regimen. Stratum 2: Less than 50 copies/ml; NNRTI (nonnucleoside reverse transcriptase inhibitor) in treatment regimen. Stratum 3: 50-400 copies/ml; PI in treatment regimen. Stratum 4: 50-400 copies/ml; NNRTI in treatment regimen. Clinic visits occur at regular intervals throughout the 48-week study period to determine viral load.