The purpose of this study is to see if L-756423, an anti-HIV drug, is safe to give with indinavir and if it works well at lowering the level of HIV in the blood (viral load).

All patients receive L-756423 plus indinavir plus two licensed nucleoside reverse transcriptase inhibitors (NRTIs), at least one to which the patient is naive. Patients remain on the drug regimen for 12 weeks (with possible extension to 16 weeks). Patients are evaluated with physical examinations and laboratory tests for blood and urine at Weeks 1, 2, 4, 6, 8, and 12 and two weeks post study. Plasma viral RNA is measured at Weeks 1, 2, 4, 6, 8, and 12. CD4 cell counts are measured at Weeks 2,4,8, and 12.

Inclusion Criteria

You may be eligible for this study if you:

• Are HIV-positive.
• Are at least 18 years old.
• Have a viral load of at least 1,000 copies/ml.
• Have a CD4 cell count of at least 100 cells/mm3.
• Have experienced treatment failure (your viral load increased significantly) within 24 weeks of study entry while taking indinavir.

Exclusion Criteria

You will not be eligible for this study if you:

• Are taking nonnucleoside reverse transcriptase inhibitors (NNRTIs).