[AS PER AMENDMENT 10/2/97: Patients assigned to the NFV arm who develop a significant intolerance may switch to RTV or IDV; those assigned to the RTV arm who develop a significant intolerance are encouraged to switch to IDV (NFV allowed if IDV contraindicated). Switchover for intolerance is strongly discouraged during the first 4 weeks of follow-up. Patients initially assigned to NFV therapy who experience disease progression may switch to RTV; if RTV is not tolerated, patients may switch to IDV. Because of the cross-resistance between RTV and IDV, patients who progress on RTV should switch to NFV.] [AS PER AMENDMENT 12/15/98: Patients originally assigned to NFV who experience poor virologic control or disease progression should change to RTV or IDV or enroll in the PIP protocol (CPCRA 057). Conversely, patients originally assigned to RTV should change to NFV or enroll in the PIP protocol (such patients continue to be followed on this study). Because of cross-resistance between RTV and IDV, change from RTV to IDV is discouraged. Determination of poor virologic control or disease progression is at the discretion of the patient's clinician. Change in background antiretroviral therapy should occur at the same time that the protease inhibitor is changed for poor virologic control or progression; the choice of new background antiretroviral agents is at the discretion of the clinician.] Randomization is stratified by clinical site.] [AS PER AMENDMENT 3/11/98: SUBSTUDY CPCRA 045: At least 600 patients (>= 400 from CPCRA sites and >= 200 from CTN sites) will be enrolled in the substudy. These patients will have a plasma sample collected for HIV RNA and genotypic resistance within 30 days prior to randomization, at the 1-month visit, and at the q-4-month study visits thereafter until the end of the study. CD4+ cell counts will be done at the 1-month visit and at the q-4-month study visits until the end of the study. A subset of patients will also have immunophenotyping of CD4+ and CD8+ cell TCR V-beta clones carried out before and during treatment. Another subset of patients at selected sites will have viral cultures performed for phenotypic drug sensitivity testing.