The study was designed to investigate the effects of Mixture of Yukgunja-tang and Bambusae Caulis in Liquamen (YTBCL) on the change of regional cerebral blood flow (rCBF) and mean arterial blood pressure (MABP) in rats, and further to determine the mechanism of action of YTBCL. The results in rats were as follows ; YTBCL 25 ${mu}l$ significantly decreased rCBF and MABP compared with basal condition. YTBCL 100 ${mu}l$ significantly increased rCBF compared with basal condition, but decreased MABP compared with basal condition. YTBCL 50 ${mu}l$ significantly increased rCBF compared with basal condition, but MABP was somewhat decreased compared with basal condition. The VTBCL 50 ${mu}l$-induced increase in rCBF was significantly inhibited by pretreatment with methylene blue (10 ${mu}g$/kg, i.p.), an inhibitor of guanylate cyclase and indomethacin (1 mg/kg, i.p.), an inhibitor of cyclooxygenase. The YTBCL 50 ${mu}l$-induced decreased MABP significantly increased by pretreatment with methylene blue but was inhibited by indomethacin. This results were suggested that the mechanism of YTBCL was mediated Dy guanylate cyclase.