Dr. Dan Stein and colleagues from Albany Medical Center in New York reported the long term data from Merck trial 021, a study which compared three doses of indinavir (800 mg thrice daily, 1000 mg thrice daily and 800 mg every 6 hours) in an antiretroviral experienced patient population with CD4 counts between 150 and 500 and HIV RNA titers > 20,000 copies/ml. Fifty six patients with average baseline CD4 counts of 240 and HIV RNA levels of 4.59 logs were randomized to one of the three dosage arms and followed for 96 weeks. For the first year the patients were maintained on indinavir monotherapy, and zidovudine was added during the second year. The percents of patients with undetectable viral were 30%, 61.5% and 58.3%, respectively. The median viral load reductions were 1.34, 1.64 and 1.85 logs, respectively. In regards to CD4 count elevations, the 3 arms had rises of CD4 cells greater than 150 at 96 weeks, with average rises of 150, 230 and 230 respectively. Six patients discontinued therapy; 3 due to nephrolithiasis, one due to taste perversion, two due to hyperbiirubinemia and one due to thrombocytopenia. Overall, 13 of 56 (23%) experienced nephrolithiasis, although after adequate hydration was instituted, the incidence of renal stones declined. This is the longest term study of indinavir therapy,which demonstrates the durability of the antiretroviral and immune boosting effect of this protease inhibitor in antiretroviral experienced patients.