Maraviroc is the first commercialized CCR5 inhibitor for HIV therapy. A new high-performance liquid chromatography-ultraviolet method to quantify maraviroc concentrations in human plasma was developed and validated. The method is based on a protein precipitation procedure, with an acidic solution of acetonitrile (trifluoroacetic acid 0.1%) and quinoxaline as internal standard. The analytes were eluted using a gradient run in 15 minutes on an analytical C18 Luna column (150 mm x 4.6 mm ID) with a particle size of 5 mum. Maraviroc and internal standard were detected by UV at 193 nm and 352 nm, respectively. The calibration curve was linear up to 2500 ng/mL. The mean recovery of maraviroc was 96%. All validation data were in accordance with U.S. Food and Drug Administration requirements. The new high-performance liquid chromatography-ultraviolet method reported here could be used routinely to monitor plasma concentrations of maraviroc in healthy volunteers and HIV-infected patients.