Three cases of primary brain tumors simulating purulent meningitis have been described. Two patients were infants suffering from ependymoma of the posterior fossa, while the third was a 35-year-old man with astrocytoma of the temporal lobe. All cases were characterized by acute onset with fever, signs of meningeal irritation without any other neurological signs, and marked CSF pleocytosis. The diagnosis in 2 cases was made only at necropsy, and the third case was correctly diagnosed only after a delay. The possible occurrence of brain tumor and meningitis simultaneously was considered and seemed unlikely in our cases. A possible explanation for the clinical and CSF findings was irritation of the leptomeninges by the tumor and its breakdown products.