334 necropsy reports of intracranial neoplasm from an autopsy material over 13 years were reviewed to study the relationship of intracranial tumors to vascular thrombosis. The incidence of venous thrombosis in intracranial tumors was found to be 27.5% while that of a control group without malignancies taken at random from the autopsy material was 17%. The difference gives a statistical significance of P less than or equal to 0.05. The parameters of sex, surgical intervention, the malignancy and the histological type of the tumor apparently dod not affect thrombus formation to a statistically significant degree. There is increased thrombosis frequency with increasing age. The presence of hemiparesis or hemiparalysis does not affect the incidence of thrombosis. However, it determines to a great degree the lateralization of the thrombus.