The authors report the case of a young boy with macrocephaly, cerebellar symptoms and signs of raised intracranial pressure. Magnetic resonance imaging showed obstruction of the aqueduct, ventricular enlargement of the cerebellum and areas of increased signal intensity in the cerebellar and frontal white matter. A stereotactic biopsy of the cerebellum showed many Rosenthal fibres and glial proliferation. Although the histopathological and neuroradiological findings were suggestive of Alexander's disease, the initial presentation and clinical course were unusual for this diagnosis. The authors suggest that a separate form of Alexander's disease should be distinguished with predominant clinical, neuroradiological and neuropathological cerebellar involvement. This form also seems to have a better life-expectancy.