BACKGROUND: The increased risk of abacavir in cardiovascular disease (CVD) in HIV-infected patients is still being debated. Maraviroc, a CCR5 blocker, has been shown to decrease immune activation and monocyte infiltration in atherosclerotic plaques in murine experiments. Therefore, we examined the effect of maraviroc intensification on flow-mediated dilatation (FMD) in abacavir-treated HIV-infected patients and its effect on immunological and inflammatory parameters. METHODS: A open-label prospective crossover study with a duration of 16 weeks: 8 weeks of intervention (maraviroc intensification) and 8 weeks of control (unchanged cART regimen). FMD, HIV-specific variables, expression of HIV co-receptors, markers of inflammation and coagulation and cellular markers of immune activation were measured at weeks 0, 8 and 16. The changes (Δ) in these variables were compared between intervention and control periods using non-parametric tests. To evaluate the relation with the change in FMD, linear regression modeling was used. RESULTS: Twenty-one male patients with suppressed plasma HIV-RNA, on cART, had a known HIV infection for 9.2 years (IQR 6.9-13.5) with abacavir use for 6.5 years (2.8-9.3). A significantly increased FMD of 0.73% (IQR -0.25 to 1.70) was seen after maraviroc intensification compared to a decrease of -0.42% (IQR -1.89 to 0.25; p = 0.049) in the control period. There was a negative relation between ΔFMD with ΔD-dimer (β -22.70, 95% CI -39.27; -6.13, p = 0.011) and ΔCD95+ CD4+ T cells (β -0.16, 95% CI -0.28; -0.04, p = 0.013), adjusted for age and duration of HIV. CONCLUSION: Maraviroc intensification modestly improves endothelial function in HIV-infected patients on an abacavir-containing regimen. TRIAL REGISTRATION: NCT01389063.