Male Alzheimer's disease patients, studied with 18-fluoro-2-deoxyglucose positron emission tomography while performing a verbal memory test, showed a right-greater-than-left asymmetry of cortical metabolism that tended to be greater than that in healthy, age-matched control subjects. This asymmetry was absent in female patients, preliminarily suggesting a propensity for left hemispheric involvement in the Alzheimer's disease process in males.