Local blood flow and capillary permeability of the rats with meningeal carcinomatosis were studied with macroautoradiography, and relationship between blood flow, permeability and effects of chemotherapy is discussed. Experimental meningeal carcinomatosis was induced in the Wistar rats by inoculating Walker 256 tumor into cisterna magna. One to 12 days after inoculation, rats were used for measurements of blood flow (by 14C- iodoantipyrine) and capillary permeability (by 14C-alpha-aminoisobutyric acid). Images of autoradiography and corresponding histological appearances were analyzed. In the early stage of tumor growth (2 to 3 days after inoculation), a few layers of tumor cells were identified in the ambient cistern. Blood flow in the vicinity of the tumor cell layer was noted, but no increase in capillary permeability was found. In the middle stage of tumor growth (3 to 5 days after inoculation), 10 to 20 layers of the tumor cell was noted in the ambient cistern. Blood flow in the tumor was evident and capillary permeability began to increase. In the late stage of tumor growth (6 to 12 days after inoculation), a mass of the tumor cells was noted in the ambient cistern. In this stage, blood flow in the tumor was similar to that of cerebral gray matter and capillary permeability increased markedly. Brain adjacent to the tumor also showed increase in capillary permeability. The result correlated well to the previous result of experimental chemotherapy. Form those data, lipid soluble drugs which cross blood-brain barrier readily are recommended for the early stage of meningeal carcinomatosis, and water soluble drugs which has limitations to cross blood-brain barrier can not be recommended.(ABSTRACT TRUNCATED AT 250 WORDS)