1. Background and Purpose For many years, Sibimikwanjungtang, Yangkyeoksanhwatang and Hyeongbangsabaeksan have been used as a therapeutic agent in constitutional disease. The effects of three prescriptions on the vascular system is not well-known. The purpose of this study is to determine the effects of these prescriptions on blood pressure(BP) and regional cerebral blood flow(rCBF). 2. Methods I injected a vein of rat with extracts of Sibimikwanjungtang, Yangkyeoksanhwatang and Hyeongbangsabaeksan with five kinds of dose and measured BP and rCBF. 3. Results After injected Sibimikwanjungtang, BP was not changed but rCBF was increased in a dose-dependent manner. After injected Yangkyeoksanhwatang, BP was elevated and rCBF was increased in a dose-dependent manner. After injected Hyeongbangsabaeksan, BP was not changed but rCBF was increased in a dose-dependent manner.