This is a randomized, open-label, active-controlled, parallel-group, multi-center study of vicriviroc maleate in treatment-naïve subjects infected with CCR5-tropic HIV. The study will compare the virologic benefit of vicriviroc combined with ritonavir-boosted Reyataz to a control group receiving Truvada plus ritonavir-boosted Reyataz. Interim analyses will be performed when the first cohort of 80 subjects have completed 24 weeks and 48 weeks of treatment. The second cohort of 120 subjects will be enrolled after the first interim analysis; a third interim analysis will be performed when subjects in this second cohort have completed 24 weeks of treatment. The primary efficacy analysis will be conducted when all 200 subjects from both stages have completed 48 weeks of treatment or discontinued. The final analysis will be performed at Week 96, when all 200 subjects have completed 96 weeks of treatment or discontinued. If vicriviroc is shown to provide benefit at the studied dose, study participants in the vicriviroc arm who complete 96 weeks of treatment may continue in a protocol extension, where they will be offered vicriviroc free of charge until the drug is commercially available in their location or until the sponsor terminates the clinical development of vicriviroc.