The aim of this study was to determine the endothelial function in patients with primary Sjögren's syndrome (SS). We also aimed to determine whether endothelial (dys)function correlates with extraglandular manifestations, specific autoantibodies and the severity of salivary gland involvement of SS. Endothelium-dependent vasodilation and endothelium-independent vasodilation of the brachial artery were assessed by a high-resolution ultrasound on 25 patients with primary SS and on 29 healthy controls. Patients with primary SS had significantly less mean endothelium-dependent vasodilation than did controls (3.0 +/- 0.4% vs 4.2 +/- 0.3%; p = 0.012). Endothelium-independent vasodilation induced by sublingual glycerol trinitrate was not different between the two groups (12.9 +/- 1.4% vs 14.1 +/- 1.2%; p = 0.86). We concluded that endothelium-dependent vasodilation was impaired in primary SS patients, in particular those presenting with Raynaud's phenomenon, when compared with the healthy controls and this impairment was not associated with the presence of RF, ANA, anti-Ro/SS-A, anti-La/SS-B and with the other extraglandular manifestations of the disease.