Objectives : The purpose of this investigation is to evaluate the effect of Geupoongjibo-dan Extracts on Reversible Forebrain Ischemia in Mongolian Gerbils. Methods : The change rate of water content in cerebral tissues, the numercal change of the CA1 pyramidal neuron in the hippocampus, the change of delayed neuronal death(necrosis apoptosis) through light microscopy, the reactivity change of glycoprotein in neuronal membrane and the ultrastructural change of pyramidal neuron through electron microscopy caused by dalayed neuronal death were investigated. Results : 1. The change rate of water content in the normal group showed 78.90% on the third day, and 79.12% on the seventh day after an attack of ischemia. The rate in the control group showed 82.25% and 85.13%, respectively. The rate in the sample group showed a significant decrease: 81.72% and 83.66%. 2. Light microscopy revealed that the cells, continuous and systematic forms in the pyramidal cells of hippocampus, changed into discontinuous and unsystematic forms in the normal group when compared with the control group. The cells were less damaged in the sample group. 3. The mean of the numerical change of the CA1 pyramidal neurons in the hippocampus was 104 in the normal group. The mean of the control group was decreased to 27. The mean of the sample group was 44. 4. TUNEL staining examination reveals that the whole part of the hippocampus of the normal group had negative reactivity. As far as CA1 pyramidal neurons in the hippocampus, the control group had positive reactivity. The sample group was more positive than the control group. 5. Electron microscopy reveals that the ischemic injury of the control group had both necrotic and apoptotic morphology. The sample group was less necrotic, and more apoptotic morphology than the control group. 6. Lectin histochemisrical examination reveals that the normal group had positive reactivity to PNA and SBA in interneuron, and weak positive reactivity to WGA Con A LCA in intercelluar space. The reactivity to PNA and WGA decreased in the control group. The reactivity to PNA and WGA tended to increase in the sample group. Conclusions : The data shows that the effect of Geupoongjibo-dan Extracts on Reversible Forebrain Ischemia in MG is a significant result.