The aim of this study was to compare the prevalence of pathologically and clinically documented thyroid disorders in patients with Alzheimer's disease (AD) and nondemented individuals. We reviewed the records of 31 patients with a pathological diagnosis of AD and 31 age-matched nondemented patients selected from autopsy files. We examined the pathological findings in the thyroid gland in both groups. Twenty-four cases (77.4%) with AD and 21 patients (67.7%) in the control group showed pathological abnormalities in the thyroid gland. The prevalence of specific types of thyroid gland abnormalities on pathological examination did not differ significantly between the AD and nondemented cases. For the 19 AD and 18 control patients in whom clinical thyroid function had been documented adequately during life, the percentage of patients with abnormal thyroid function was similar in the AD (15.7%) and control (11.1%) groups. These results do not support a relationship between AD and thyroid abnormalities.