Dietary intervention and simvastatin is beneficial in the prevention cardiovascular diseases by lowering plasma lipid levels. Endothelial dysfunction is associated with coronary artery disease and its risk factors and is reversed by dietary intervention. It has been suggested that hyperlipidemia contributes to the development of atherosclerosis by increasing inducible nitric oxide synthase (iNOS) expression via intimal thickening. Statins treatment has been found to decrease iNOS expression and atherogenensis in animal models. We hypothesized that dietary intervention and simvastatin therapy could decrease plasma nitric oxide in hypercholesterolemic patients, which would suggest the opportunity for modulation of iNOS expression through the use of statins in a clinical situation. We measured the plasma levels of nitrite and nitrate (NOx) in 19 hyperlipidemia patients. The subjects were under dietary intervention following simvastatin therapy for 12 weeks. As a result, the plasma level of NOx, stable metabolites of nitric oxide (NO), saw a two-fold elevation in hyperlipidemic patients as compared to normal levels. Although 12 weeks of dietary intervention did not lower NOx levels, subsequent 12-week simvastatin (10 mg/day) treatment, along with dietary intervention, lowered NOx levels significantly. This NOx reduction, induced by simvastatin therapy, positively correlated with lowered coronary risk factors (r=0.40, p=0.02). It indicated that simvastatin therapy decreases plasma NOx levels by, perhaps, decreasing iNOS expression or activity leading to the attenuation of the development of neointima.