This experimental study was designed to investigate the effects of Sagunja-tang(SGJT), Ijin-tang(IJT), Yukgunja-tang(YGJT) on the change of cerebral hemodynamics [regional cerebral blood f1ow(rCBF), mean arterial blood pressure(MABP), and pial arterial diameter (PAD)] in normal rats, and further to determine the mechanism of action of YGJT. And, this Study was designed to investigate whether YGJT inhibit lactate dehydrogenase(LDH) activity in neuronal cells. The results were as follows ; 1. SGJT significantly increased rCBF but MABP was not changed comparing with normal MABP(l00 %). This results were suggested that SGJT significantly increased rCBF by dilating PAD. 2. IJT significantly decreased rCBF in a dose-dependent, but significantly increased MABP in a dose-dependent. This results were suggested that IJT significantly decreased rCBF by contracting PAD. 3. YGJT significantly increased rCBF and PAD in a dose-dependent, and YGJT increased MABP compared with normal MABP(100 %). This results were suggested that YGJT significantly increased rCBF by dilating PAD. 4. The YGJT-induced increase in rCBF was significantly accelerated by pretreatment with indomethacin (IDN, 1 mg/kg, i.p.), an inhibitor of cyclooxygenase but was significantly inhibited by methylene blue (MTB, 10 ㎍/㎏ i.p.), an inhibitor of guanylate cyclase. 5. The YGJT-induced increase in PAD and MABP were accelerated by pretreatment with IDN but was significantly inhibited by MTB. This results suggested that the mechanism of YGJT is mediated by guanylate cyclase. 6. YGJT inhibited significantly LDH activity in neuronal cells. This results were suggested that YGJT prevented the neuronal death. I thought that YGJT should have improvement of cerebral hemodynamics and inhibitive effect on the brain damage.