The association between findings on the neurologic examination and the clinical diagnosis of Alzheimer's disease was investigated among 467 individuals from a geographically defined community population. Participants were selected by stratified random sampling based on their memory performance in a population survey of community residents 65 years of age and older. Each participant underwent a structured medical, psychiatric, neurologic, and neuropsychologic examination. Of the 467 persons examined there were 134 cases of probable Alzheimer's disease and 167 control subjects. Multiple logistic regression analysis was used to estimate the degree to which the presence of each of several neurologic examination findings affected the age- and sex-adjusted relative odds of having clinically diagnosed Alzheimer's disease. The most striking associations with the diagnosis of Alzheimer's disease were seen with various measures of extrapyramidal dysfunction. These increased relative odds were not markedly affected by excluding from the analysis cases with severe cognitive impairment. The results suggest that involvement of the extrapyramidal system is a common finding in Alzheimer's disease.