This Study was designed to investigate the mechanism of Prescription for Treatment Abundant Expectoration due to Deficiency of Qi(Yukgunja-Tang, YGT) on cerebral hemodynamics [regional cerebral blood f1ow(rCBF) and pial arterial diameter(PAD)] in cerebral ischemia rats. The results were as follows: Both rCBF and PAD were significantly and stably decreased by YGT (10㎎/㎏, i.p.) during the period of cerebral reperfusion, which contrasted with the findings of rapid and marked increase in Control group. Pretreatment with indomethacin(1㎎/㎏, i.p.), an inhibitor of cyclooxygenase and methylene blue(10㎍/㎏, i.p.), an inhibitor of guanylate cyclase significantly but unstably increased the YGT-induced increases in rCBF during the period of cerebral reperfusion. Pretreatment with indomethacin significantly and stably decreased the YGT-induced increases in PAD during the period of cerebral reperfusion, but pretreatment with methylene blue increased unstably the YGT-induced increases in PAD during the period of cerebral reperfusion. In conclusion, the present authors thought that mechanism of YGT on cerebral hemodynamics was connected with guanylate cyclase in cerebral ischemia rats.