We compared the tumor uptake of 11C-methionine (MET) with positron emission tomography (PET) with the results of a pathological analysis to examine the proliferative potential and microvessel density measured with immunostaining for MIB-1 and factor VIII, respectively, from 33 patients with glioma. The MET uptake in oligodendrogliomas was significantly greater than that in grade 2 astrocytomas and comparable to those in grade 3 and 4 astrocytomas. The MIB-1 index of oligodendroglioma meanwhile was comparable to that of grade 2 astrocytoma. The microvessel area in oligodendroglioma was significantly greater than that in grade 2 astrocytomas and comparable to those in grade 3 and 4 astrocytomas. According to a multivariate statistical analysis, MET uptake ratio was closely correlated with the MIB-1 index among astrocytomas. An increase in the microvessel area in the oligodendrogliomas contributed to the higher MET uptake among the tumors with a low-proliferative index. This information is important for interpreting the results of MET-PET studies for clinical use.