Leptomeningeal gliomatosis is a primary glioma residing mainly in the leptomeninges. We describe a rare case of diffuse leptomeningeal glioma, occurring in a six year old girl, in which the morphological features of the cellular infiltrates were those of an oligodendroglioma. To our knowledge, this is the fifth case of diffuse oligodendrogliomatosis reported in the English language literature.