The effects of Choto-san on microcirculation, serum nitric oxide and lipid peroxides were investigated. Fifteen patients with asymptomatic cerebral infarction were investigated before and after a four-week administration of Choto-san. The variables of microcirculation of the bulbar conjunctiva, which were the internal diameter of vessels, flow velocity and flow volume rate, were increased. Serum NO2(-)/NO3(-) tended to increase and lipid peroxides were decreased. Total serum cholesterol was also decreased. These results suggest that Choto-san may improve microcirculation affected by endothelial function and fat metabolism.