Cholesterol lowering involving different therapies improves the clinical outcome of patients. To define the underlying pathomechanism, we studied whether treatment with statins was associated with changes in blood thrombogenicity, endothelial dysfunction and soluble adhesion molecule levels. Fifty hypercholesterolemic patients were treated with pravastatin (40 mg/day, n=24) or simvastatin (20 mg/day, n=26). Lipid profile and blood thrombogenicity were assessed in all patients before and after 3 months of cholesterol reducing therapy. Blood thrombogenicity was assessed as thrombus formation, perfusing non-anticoagulated blood directly from the patients' vein through the Badimon perfusion chamber (shear rate 1690/s). Endothelial-dependent vasomotor response was tested by laser-Doppler flowmeter. Soluble adhesion molecule level were measured by ELISA. Total and LDL cholesterol were reduced in the two treatment groups by statin therapy. Statin therapy was associated with a significant reduction in blood thrombogenicity and endothelium-dependent vasoresponse. No differences were observed between simvastatin or pravastatin treatment. Lipid lowering by statins had no effect on plasma levels of fibrinogen, sL-selectin, sP-selectin and sICAM-1 antigen. Cholesterol lowering by both statins reduced the increased blood reactivity and endothelial dysfunction present under hypercholesterolemia. The multiple effects of lipid lowering therapy by statins may explain the benefits observed in recent epidemiological trials.