Initially, specimens for 50 randomly chosen patients in the group originally assigned RTV will be identified for resistance testing. Of this group, specimens for those who have received RTV/IDV for more than 1 month will be analyzed for genotypic resistance to obtain an estimate of the rate of resistance development and to estimate the risk of disease progression associated with resistance to RTV/ZDV. Based on these estimates, determination will be made of the total number of patients and specimens in both treatment groups in order to address the primary objective of comparing genotypic resistance in the two groups.]