SAENGMAEGSAN(SMS) has been used in oriental medicine for many years as a therapeutic agent for cerebral disease. The effect of SMS on the vascular system is not known. The purpose of this study was to determine the effect of SMS on blood pressure, regio-nal cerebral blood flow(rCBF). 1. Blood pressure did not change by SMS in rats. 2. rCBF was increased by SMS in a dose-dependent manner. 3. Pretreatment with propranolol. methylene blue and indomethacin significantly inhibited SMS induced increase in rCBF. These results suggest that SMS causes a diverse response of blood pressure, regional cerebral blood flow (rCBF) and pial arterial diameter. The increase in rCBF is also mediated by prostaglandins. cyclic GMP and adrenergic ${eta}$receptor.