Effective chemotherapy and radiation therapy of brain tumors require knowledge of the cerebral circulatory dynamics involved. In this study, regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), and regional cerebral capillary permeability (rCP) were measured in Wistar King Aptekman rats bearing experimental KEG-1 gliomas. These parameters were assessed by autoradiography with 14C-iodoantipyrine, 14C-deoxyglucose-labeled red blood cells, and 14C-aminoisobutyric acid, respectively. rCBF within the tumor was approximately one third that in the contralateral cortex and was consistently higher in the periphery than in the center of the tumor. In the periphery of the tumor, rCBV was approximately twice that in the contralateral cortex, but it was very low in the center of the tumor. Throughout the tumor, rCP was sharply increased relative to that measured in the contralateral cortex, and the increase was especially pronounced in the central portion. Thus, rCBF, rCBV, and rCP each appeared to vary within the tumor, implying that the combined use of lipid- and water-soluble chemotherapeutic agents is reasonable. Measurement of these parameters may also provide indices of radiation sensitivity.