One of the major indicators of intact endothelial function is basal nitric oxide (NO) activity. Further, it seems to be likely that statin therapy exerts beneficial effects on vascular function, at least in part via an improvement of NO bioavailability. In the present double-blind crossover study 29 hypercholesterolemic patients were randomly assigned to receive rosuvastatin and placebo for 42days. Pulse wave analysis was assessed after 30min of rest (baseline) and after infusion of N G-monomethyl-l-arginine (l-NMMA) at the end of 42days treatment period. The magnitude of the increase in central augmentation index (cAIx) in response to inhibition of NO synthase (NOS) by l-NMMA is indicative of basal NO activity. CAIx was significantly lower (18.3±10 versus 21.9±12%, p=0.027) with rosuvastatin compared to placebo. There was no increment of cAIx in response to l-NMMA in placebo group. In contrast, cAIx increased significantly in response to l-NMMA (20.5±11 versus 25.7±10mm Hg, p=0.001) in rosuvastatin group. The percentage of increase of cAIx tended to be more pronounced after treatment with rosuvastatin compared to placebo (53.7±92 versus 14.1±36%, p=0.087). Pulse pressure amplification (PPA) improved (1.31±0.2 versus 1.26±0.2%, p=0.016) after rosuvastatin compared to placebo. Regression analyses revealed that both LDL-cholesterol and CRP-levels are independent determinants of basal NO activity improvement, which itself is an independent determinant of vascular function, expressed by an improvement of pulse wave reflection and PPA. In this placebo controlled study, treatment with rosuvastatin improved vascular and endothelial function. Determinants for improved NO production in patients with hypercholesterolemia were the achieved levels of LDL-cholesterol and CRP. Overall, in patients without CV disease, rosuvastatin exerted beneficially effect on vascular dysfunction, one of the earliest manifestation of atherosclerosis.