The cerebellum is a relatively neglected area of the Alzheimer's disease (AD) brain, probably because it was formerly thought to be spared by the disease. However, a number of pathological changes have now been revealed in the AD cerebellum, principally by immunocytochemical studies, including widespread deposits of diffuse amyloid, ubiquitin-immunoreactive dystrophic neurites, and increased microglia, but tau-immunoreactive neurofibrillary tangles have not been seen. Although the observed changes may be merely epiphenomenal to the pathological processes occurring in the AD neocortex and hippocampus, the morphological and immunocytochemical differences between AD cerebral cortex and cerebellar cortex may nonetheless give insights into the molecular factors involved in the development of the neuropathological lesions of AD brain.