201Tl-SPECT was performed in 25 patients with a pathological diagnosis of glioma. The lesion-to-normal (L/N) ratio of the glioblastoma group (n = 7) was found to be higher than that of the low-grade glioma group (n = 7; Mann-Whitney U-test, p < 0.0167). 201Tl accumulation in the tumor corresponded to contrast enhancement on MRI in 95% of cases. An insufficient blood-brain barrier was considered to be the primary contributor to 201Tl accumulation. In five cases, there was a discrepancy between the extent of 201Tl accumulation and the Gd-DTPA enhanced area. In these cases, the area of 201Tl accumulation was larger than the area of Gd-DTPA enhancement. This may result from damage to the blood-brain barrier that is not severe enough to be detected with Gd-DTPA or from additional factors other than change in the blood-brain barrier. 201Tl-SPECT is able to demonstrate the extent of glioma more accurately than contrast-enhanced MRI.