Following genotypic screening at baseline, qualifying subjects will be randomized to one of three blinded treatment regimens. Subjects will discontinue their current protease inhibitor and initiate TPV/RTV for 2 weeks of functional monotherapy. Thereafter, the background ARV medications will be optimized and subjects will remain on blinded TPV/RTV plus optimized background therapy for the duration of the trial. Trial duration ranges between 12-32 weeks, depending on when the subject is entered into the trial and the interim analyses for determination of optimized TPV/RTV regimen is completed. On determination of the optimal TPV/RTV dose, subjects may opt to continue open-label treatment.