Three children, aged 4, 5, and 9 years, had an insidious onset of ataxia. Magnetic resonance imaging (MRI) showed hydrocephalus and countless foci of high T2 signal coating the cerebellum, basilar cisterns, brainstem, and fourth ventricle. Similar lesions were present in the spinal cord. Symptoms were relatively mild given the massive tumor burden. Biopsies were composed of superficially infiltrating cells with oligodendroglioma-like features (perinuclear halos and cytologic monotony) and microcysts. Classical cytogenetic analysis of 2 cases showed normal karyotypes. Chromosome fluorescence in situ hybridization revealed 1p36 deletion with intact 19q in 2 cases and no abnormality in one. A similar combination of clinical, MRI, and histopathologic findings has been reported previously in 10 other cases. The pathologic findings suggest a glioma with diffuse or multifocal superficial origin and do not correspond to a described entity in the current World Health Organization (WHO) classification of brain tumors.