This is a 48 week study that is intended for HIV Infected persons whose first treatment regimen was with a nonnucleoside reverse transcriptase inhibitor (NNRTI) and who are now failing that regimen. They must be currently on their failing regimen to be eligible.

Inclusion Criteria:

• Male or female at least 18 years old
• HIV RNA level >1000 copies/mL at screening
• CD4 >50 cells/uL at screening
• Patient is currently taking a regimen that includes an NNRTI plus 2 NRTIs for at least 28 days and is currently failing this regimen
• Patient has adequate hematology tests (absolute neutrophil count >1000/uL, Platelets>75,000uL, hemoglobin 9g/L)
• Patient has adequate renal function (serum creatinine of <1.5 upper limit of normal)
• Patient has adequate liver function (AST, ALT, and bilirubin < 2.5 upper limit of normal)

Exclusion Criteria:

• Previous use of protease inhibitors (except if patient has short duration of PI and was switched for tolerability reasons when viral load was <50 copies) This exception does not include Viracept
• Women who are pregnant or lactating