Findings from T2-weighted magnetic resonance (MR) images obtained of postmortem, in vitro human brain glioma specimens were correlated with histologic findings from whole-brain sections. Eighteen cases were categorized as untreated (n = 6), in remission after surgery and radiation therapy (n = 2), or recurrent (n = 10). Findings from MR images generally correlated well with the histologic extent of untreated tumors in white matter; the heterogeneous appearance of glioblastomas multiforme distinguished them from less malignant gliomas. Subpial spread and tumor in the subarachnoid space were not visualized. The extent of tumors in remission was overestimated on MR images because of the extensive surrounding edema and radiation necrosis. MR imaging findings correlated well with those from 48% of brain slices, but resulted in overestimations (24%) or underestimations (28%) of tumor extent in the ten cases of recurrent tumor. The results suggest that information concerning the patient's stage of disease is important in interpreting MR images of gliomas.