Aims: To assess oxidative DNA damage and total antioxidant capacity (TAC) in glioblastoma multiforme (GBM) and to compare the results with normal brain tissues. Materials and methods: Oxidative DNA damage and TAC were evaluated in GBM tissues extracted from 26 patients and in normal brain tissues of 15 subjects who underwent autopsy within the first 4 h of death. Oxidative DNA damage was assessed by measuring 8-hydroxy-2-deoxyguanosine (8-OH-dG) using the 8-OH-dG enzyme immunoassay kit, a quantitative assay for 8-OH-dG, and TAC was analysed using the ImAnOx colorimetric test system for the determination of antioxidative capacity. The results were compared between two groups and any correlation between 8-OH-dG and TAC was sought. Results: The median level of TAC in GBM (121.5 nmol/g wet tissue) was remarkably lower than that in normal brain tissue (298 nmol/g wet tissue). The difference was statistically significant (P = 0.00001). In contrast, oxidative DNA damage was significantly higher in patients with GBM (74.9 ng/g wet tissue) than in controls (34.71 ng/g wet tissue). Again, the difference was statistically significant (P = 0.00001). We also found a negative correlation between oxidative DNA damage and TAC (P < 0.001). Conclusions: These findings indicate that the degree of oxidative DNA damage is increased and TAC is decreased in GBM. Oxidative DNA damage is correlated with the levels of TAC.