Fifteen (15.6%) patients of 97 with malignant glioma developed meningeal gliomatosis during at least 2 years after the initial treatment. The time between the first surgery and diagnosis of meningeal gliomatosis was less than 1 year in 10 cases, 1 to 2 years in 2 and over 2 years in 2. In the younger age group less than 20 years, the incidence of meningeal gliomatosis was higher (46%) than that (12%) in the older group. Despite intrathecal chemotherapy (cytosine arabinoside, bleomycin and methotrexate), all patients died 2 to 24 weeks after the diagnosis of meningeal gliomatosis. Experimental studies suggest that intrathecal ACNU may be promising for the treatment of meningeal gliomatosis.