A 66-year-old man was investigated for increasing forgetfulness and frequent falls. Following appropriate investigations, the cause was presumed to be senile dementia of the Alzheimer type. He was reviewed one year later and found to have impaired vertical gaze and a hoarse voice. Progressive dementia, nuchal rigidity, anarthria, and sphincteric incontinence developed subsequently. A diagnosis of progressive supranuclear palsy was made. He died four years after the initial assessment. Neuropathological examination revealed changes characteristic of progressive supranuclear palsy, and suggestive of Alzheimer's disease. Globose tangles, granulovacuolar bodies and gliosis were present in the midbrain, the pons, the dentate nucleus of the cerebellum, and the globus pallidus. Senile plaques and occasional neurofibrillary tangles and granulovacuolar bodies were found in the hippocampus, amygdala, and temporal cortex. The coexistence of two disease processes resulting in dementia is discussed.