This study aims to examine two management strategies, immediate versus deferred IDV therapy, for their clinical effects in the context of background antiretroviral (AR) therapy, given according to current clinical practice. There is an urgent need to identify the optimal use of IDV in patient management, since clinical endpoint studies have not been completed in the United States. Since there is little information about the long term durability of clinical effects, and even less information about the timing of the initiation of protease inhibitor therapy, exploring the disease progression and survival impact of immediate versus delayed use of IDV will yield important information to guide clinical decision making for this group of patients.