Hypercholesterolemia is linked to endothelial dysfunction and enhancement of the endogenous inhibitor of NO synthase. The statins have lipid-lowering and pleiotropic properties, which could exert protective effects on the endothelium in hypercholesterolemia. The association of L-arginine with simvastatin could promote a further improvement on endothelial function in this condition. Thus, we investigated whether simvastatin, with or without supplementation with L-arginine, could improve endothelium-dependent vasodilation. In this study, 25 hypercholesterolemic subjects were treated according to the following protocol: washout period of 1 month; simvastatin (20 mg/day) for 2 months; simvastatin (20 mg/day) + L-arginine (7 g/day) for 2 months. From these patients, 10 were chosen at random for evaluation of vascular function by high resolution ultrasonography of the brachial artery. In subjects treated with simvastatin plus L-arginine, an increase of L-arginine levels (68%) and L-arginine/asymmetric dimethylarginine (ADMA) ratio (67%) were observed. Simvastatin reduced the plasma concentrations of NO metabolites nitrite + nitrate (NOx: 34%), S-nitrosothiols (RSNO: 42%), total cholesterol (25%), low density lipoprotein (LDL)-cholesterol (36%) and the LDL-cholesterol/high density lipoprotein (HDL-cholesterol ratio (34%). Simvastatin, associated or not to L-arginine, did not affect ADMA levels and endothelium-dependent vasodilation. Our data showed that simvastatin reduced the plasma concentrations of NOx and RSNO without affecting either the levels of ADMA or endothelium-dependent vasodilation in hypercholesterolemia.