Earlier Phase II/III clinical trials indicate APV is effective in retarding HIV progression in the body. Despite these data, however, the drug has yet to receive regulatory approval. At the same time, there is an urgent need to grant pre-approval access to specific groups of patients eager to benefit from the anti-HIV potential inherent in APV. This study examines the relative effects APV has in patients with prior treatment failure or intolerance to previous protease inhibitor therapy.