Morphologic features of the autopsied specimen of 22 cases with supratentorial gliomas treated by surgery, radiation and/or chemotherapy were analysed, and the characteristics of recurrence of gliomas were searched for. The cases consisted of anaplastic 12 astrocytoma and 10 glioblastoma. The results were as follows: 1) Characteristic CT findings before death were regrowth of the tumor mass or the occurrence of a new enhanced lesion in 21 out of 22 cases. The enhanced lesion showing regrowth of the tumor located in the same site as the previous tumor mass in 21 cases. The new enhanced lesion resulting from a trans-or subependymal tumor spread, was seen in the ventricular wall, and these findings were a characteristic feature of the recurrence of gliomas. 2) Modes of extension of the tumor were subdivided into 3 types. One was the expansive or infiltrative type caused by regrowth of the residual tumor. In the second pattern, a spread of tumor cells occurred along the myelinated fiber tracts to the brain stem (60%), or to the contralateral cerebral hemisphere through the corpus callosum (50%). The third mode of tumor propagation was cerebrospinal fluid seeding with intraventricular or subarachnoid tumor regrowth (45%). 3) Characteristic histological findings shown in the original tumor bed were those of increased cellularity with endothelial proliferation, widespread necrosis with occlusion of the blood vessels, occurrence of the gemistocytic astrocytes and large bizarre cells. Thickening of wall of the blood vessels due to effect by radiation was followed by occlusion of the blood vessels. Large necrosis in the tumor tissue was caused by those process and others. Necrotic area was mainly circumscribed and corresponded to the territory of the vessels. One of the specific findings in the morphological changes of the tumor cells was giant cell formation which were monstrous cell, giant cell (12 cases out of 22), and gemistocytic cell (in all cases). These specific cells were supposed to the degenerative changes of the tumor cells exposed while withstanding such adverse conditions as hypoxia, radiation and chemotherapy. 4) Infiltration distant from the primary lesion which were defined only by microscopical examination was demonstrated as both through myelinated fiber tracts in 8 cases and through perivascular spaces in 2 cases. Reinvasion of the tumor cells from the subarachnoid spaces to the brain parenchyma was along the Virchow-Robins spaces of the penetrating blood vessels in the latter cases.(ABSTRACT TRUNCATED AT 400 WORDS)