An autopsy of meningeal leukemia developing during hematological remission was reported. A three-year-old boy with anemia, hepatosplenomegaly and lymphadenopathy was diagnosed as having acute lymphoblastic leukemia based on hematological data. The hematological remission started about a month after the initiation of anticancerous chemotherapy with Prednisone, Vincristine and 6-Mercaptoprine. About two months after the ceasing of administration of Prednisone, symptoms such as headache and vomiting become gradually more severe. The clinical diagnosis was made as aseptic meningitis. The patient expired about two months after the onset. The autopsy revealed intense leukemic infiltration in the entire meninges and a part of the brain, but no infiltration was found in the other organs including the bone marrows, spleen, lymph nodes, liver, testis, etc., at all.