To evaluate the safety and efficacy of Stribild®, a single tablet regimen (STR) containing fixed doses of elvitegravir (EVG)/cobicistat (COBI [GS-9350])/emtricitabine (FTC)/tenofovir disoproxil fumarate (TDF) versus ritonavir-boosted atazanavir (ATV/r) plus the standard of care nucleoside reverse transcriptase inhibitor (NRTI) backbone FTC/TDF (Truvada®). ATV/r + FTC/TDF was selected as the active comparator for this study as it is a preferred protease inhibitor-based regimen in guidelines for the treatment of HIV-1 infected, antiretroviral treatment-naive adults.