Olfactory dysfunction is currently not listed among the NINCDS-ADRDA clinical criteria for the diagnosis of Alzheimer's disease. There is a large amount of psychophysical and neuropathologic evidence to suggest that patients with Alzheimer's type dementia have olfactory system abnormalities. The rhinologic status of this group has not been characterized. The authors examined 21 Alzheimer's patients and 21 age-matched controls to determine whether 1. the Alzheimer's group, in fact, had a diminished sense of smell, and whether 2. rhinologic factors were responsible for this nasal dysfunction. The findings support a neurologically mediated phenomenon as the cause for significant impairment in olfactory function in patients with probable Alzheimer's disease.