Blood flow within tumors is important from the standpoint of malignant tumor chemotherapy. It is known that the degree of tissue penetration of lipid-soluble anticancer agents depends on the amount of blood flow within the brain tumor. We investigated regional cerebral blood flow in rats with brain tumors. As compared with that of normal brain, the blood flow within the tumor was low and became significantly increased by inducing a hypertensive condition. These data suggest that the combination of anticancer agent and hypertensive drug is of value to enhance the effects of chemotherapy of brain tumor.