Involvement of oxidative stress in ischemia/reperfusion-induced brain damage has been suggested. However, experimental support of this suggestion was limited partly because sensitive indices to assess oxidative consequences of ischemic brain damage were few. We have established biochemical assay systems to assess oxidative brain damage following ischemia. Mongolian gerbil brains were subjected to global ischemia/reperfusion, and the hippocampi were analyzed for oxidative damage by measuring temporal changes in glutathione and 8-ohdG following ischemia. Under oxidative stress, glutathione is known to be oxidized and subsequently depleted from cells. Therefore, glutathione content and its redox status can serve as sensitive indicators of oxidative damage. The accumulation of 8-ohdG has also been recognized as an excellent marker for oxidative DNA damage. The reduced and oxidized glutathione were measured by HPLC method following derivatization with 2,4-dinitrofluorobenzene. The 8-ohdG in DNA hydrolyzate was measured by HPLC with electrochemical detection. While total glutathione content decreased, glutathione oxidation ratio and 8-ohdG accumulation increased over a period of 30 min of reperfusion following ischemia. The results demonstrated that glutathione content, its oxidation ratio, and the accumulated 8-ohdG could be utilized as sensitive indices for the assessment of oxidative brain damage.