This study will see how safe and effective against HIV the drugs L-756423 plus indinavir (IDV) are compared to just IDV when taken with stavudine (d4T) and lamivudine (3TC). The study will also see whether taking 1 large dose of L-756423/IDV once a day is as safe and effective as taking 2 smaller doses twice a day.

Patients are randomized to 1 of 4 treatment arms. In Group 1, patients receive a dose of L-756423/IDV once daily plus IDV placebo. In Group 3, patients receive a lower dose of L-756423/IDV twice daily (with the daily dosage equaling that of Group 1) plus IDV placebo. In Groups 2 and 4, patients receive equal dosages of IDV plus L-756423/IDV placebo. In all 4 groups L-756423 and IDV are blinded to the investigator and patient. All groups receive open-label d4T and 3TC. Patients routinely undergo a physical exam and have blood and urine tests to ensure the drugs' safety and tolerability, which will be evaluated by tabulation of adverse events and clinical assessment of laboratory data. In addition, CD4+ T cell and plasma viral RNA levels are measured to quantify the drugs' antiretroviral activity.

Inclusion Criteria

You may be eligible for this trial if you:

• Have HIV infection.
• Have levels of CD4 cells of 100 cells/mm3 or greater.
• Have a viral load of 10,000 copies/ml or greater.
• Are 18 years of age or older.

Exclusion Criteria

You may not be eligible for this trial if you:

• Have ever taken anti-HIV drugs.