CT findings of meningeal carcinomatosis were studied in 17 patients (seven with lung cancer, two with breast cancer, one with gastric cancer, one with malignant melanoma, five with leukemia, and one with malignant lymphoma). The diagnosis was confirmed by a cytological survey of the cerebrospinal fluid and/or autopsy. Signs and symptoms caused by meningeal carcinomatosis at the CT examination varied from individual to individual. Those most frequently observed were signs of increased intracranial pressure, often accompanied by cranial nerve palsies, paresthesia, motor weakness, cerebellar signs, and nuchal stiffness, CT scan revealed evidence of meningeal carcinomatosis in ten cases out of the seventeen. CT evidences were obtained in 16.7% of the cases with hematologic malignancy and in 81.8% of those with non-hematologic malignancies. The CT findings of meningeal carcinomatosis may be summarized as follows: I. 1) Obliteration and narrowing of the cisterns and sulci, with contrast enhancement along them. 2) Enhanced spots/areas beneath the brain surface, with contrast enhancement. 3) Diffuse, slightly high density of the brain surface, with contrast enhancement. 4) Enhancement of the ventricular wall. 5) Hydrocephalus. II. 1) No CT abnormalities.