Maraviroc (Celsentri; Selzentry) is a CCR5 coreceptor antagonist used in the treatment of CCR5-tropic HIV-1 infection. Administered orally twice daily, maraviroc, in combination with optimized background therapy regimens, showed good virological and immunological efficacy over 48 weeks in antiretroviral treatment-experienced patients aged > or = 16 years with CCR5-tropic HIV-1 infection, in the randomized, double-blind, placebo-controlled, multicentre, MOTIVATE 1 and MOTIVATE 2 studies. Initial data indicate that the efficacy of maraviroc in this patient population is sustained for up to 96 weeks. In the MERIT study in antiretroviral therapy-naive patients aged > or = 16 years with CCR5-tropic HIV-1 infection, maraviroc was noninferior to efavirenz (each in combination with zidovudine/lamivudine) for one primary virological endpoint (HIV-1-RNA levels < 400 copies/mL), but not for the other primary endpoint (HIV-1 RNA levels < 50 copies/mL) in the primary analysis at 48 weeks. However, in a subsequent analysis, which used a more sensitive tropism testing assay than the one originally used and retrospectively excluded patients with non CCR5-tropic HIV-1 infection who were ineligible for inclusion in the study, maraviroc demonstrated noninferiority to efavirenz on both primary virological endpoints. Maraviroc showed sustained virological efficacy in this patient population and improved immunological markers for up to 96 weeks. Maraviroc was generally well tolerated by both treatment-experienced and treatment-naive patients with CCR5-tropic HIV-1 infection. Thus, maraviroc, as a component of antiretroviral combination therapy regimens, is an important option for use in treatment-experienced adults with CCR5-tropic HIV-1 infection. Available data indicate that maraviroc may also have a role in treatment-naive adults with CCR5-tropic HIV-1 infection, a population in whom CCR5-tropic HIV-1 is often the major quasispecies.