The vascular function in HIV-infected persons under HAART and non- HIV-infected persons was investigated. Method: 18 HIV-positive patients and 23 HIV-negative subjects (14 younger group and 9 older group) were evaluated for microvascular vasodilatation during postocclusive reactive hyperemia (PORH) and during prolonged local thermal hyperemia; overall microvascular fl ux increase induced by iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP); and large artery stiffness (SIDVP). Results: Cutaneous vascular conductance (CVC) responses to ACh were lower in HIV patients compared to both HIV-negative groups (mean [SEM]) (HIV positive: 878.2 [99.5]; older HIV negative: 1129.3 [231.6]; younger HIV negative: 1366.5 [172.6] % baseline). Regarding SNP iontophoresis, HIV- positive and older HIV-negative groups showed lower CVC responses than younger HIV-negative group (HIV positive: 1043.0 [164.6]; older HIV-negative: 980.8 [108.3]; younger HIV-negative: 1757.3 [245.1] % baseline). Vasodilatation induced by thermal hyperemia (HIV positive: 1.63 [0.11]; older HIV negative: 1.48 [0.08]; younger HIV negative: 1.85 [0.27] perfusion units/mm Hg) and PORH (HIV positive: 0.374 [0.025]; older HIV negative: 0.326 [0.025]; younger HIV negative: 0.326 [0.037] PU/mm Hg) were similar between all groups. SIDVP was greater in HIV and older healthy groups than younger healthy group (HIV positive: 9.17 [0.42]; older HIV negative: 8.19 [0.43]; younger HIV negative: 6.42 [0.22] m/s). Conclusion: HIVinfected patients under HAART exhibited slight but nonsignifi cant lower microvascular reactivity to pharmacological stimuli and increased arterial stiffness compared to age-matched HIV-negative subjects. Comparison of both HIV-positive and older HIV-negative groups with younger HIV-negative subjects suggests that age plays a major role in microvascular reactivity regardless the HIV-infection.