Aim To study the effect of hypercholesterolemia (HC) on platelet quantitative stereologic parameters and its change after treatment by pravastatin. Methods 20 patients with HC were selected and treated with pravastatin 10～20 mg/d for 4～8 weeks. The changes of platelet ultrastructure were observed by electron microscopic and analysed with quantitative stereologic method. Results After 4～8 weeks treatments, the levels of serum total cholesterol (TC) and platelet aggregation function were lowered and most of platelet quantitative stereologic parameters were improved. Conclusion Altered platelet function and quantitative stereologic parameters with pravastatin therapy in patients with HC can be corrective with its mechanism of enhancing atherosclerosis regression.