Objectives: The present study was carried out to investigate the effects of Yupoongyangyeong-tang(YYT) on changes of regional cerebral blood flow (rCBF) and mean arterial blood pressure (MABP) in rats. In addition, the author also investigated action mechanisms of YYT on changes in rCBF and MABP. Methods and Results : In this study, treatment with YYT elevated rCBF in a dose-dependent manner, but MABP levels were elevated only in the 10 mg/ml treatment group. Pre-treatment with indomethacin. an inhibitor of cyclooxygenase, inhibited increase of rCBF effectively. Pre-treatment with methylene blue, an inhibitor of guanylate cyclase, inhibited increase of rCBF induced by YYT, too. In addition. pre-treatment with indomethacin also inhibited increase of MABP. However, pre-treatment with methylene blue did not affect MABP levels. Conclusion : These results suggest that YYT is useful to treat patients with diseases related to cerebral ischemia, because YYT can increase rCBF. In addition, the mechanisms are thought to be related to both cyclooxygenase and guanylate cyclase.