We studied the incidence of computed tomography evidence of cerebellar atrophy in 20 elderly patients with dementia, 20 age-matched controls, and 40 younger normal subjects. Cerebellar vermian atrophy was present in 6 of 20 demented patients, 7 of 20 elderly controls, and 1 of 40 younger controls. There was no other atrophy of infratentorial structures except for occasional enlargement of the cisterna magna and cerebellopontine angle cisterns. Vermian atrophy did not correlate with cerebral atrophy (enlargement of either lateral ventricles or cortical sulci). None of these patients had clinical signs of cerebellar dysfunction. Therefore, atrophy of the cerebellar vermis may occur selectively with aging, without atrophy of the cerebral cortex, and without clinical manifestations.