A phase II randomized, controlled, partially blinded, trial to investigate dose response of TMC114/RTV in HIV-1 infected patients who have previously received all three licensed classes of HIV antiviral drugs (known as nucleoside reverse transcriptase inhibitors (NRTI), nonnucleoside reverse transcriptase inhibitors (NNRTI) and protease inhibitors (PI)), and who are on a stable PI-containing regimen not including an NNRTI may be eligible to participate. Four doses of TMC-114/ritonavir will be studied. 300 patients in the United States and Puerto Rico will participate. The duration of the study is 96 weeks. Randomize to one of 4 treatment groups (TMC114/RTV: 400/100 mg qd; 800/100mg qd; 400/100mg bid; 600/100 bid) or control arm for 24 to 48 wks. Optimal dose (TMC114/RTV 600/100mg bid) open label portion of the study. The trial was extended to include 144Wks of treatment.