Erythrocytes from patients with Alzheimer's disease show signs of disturbance of the normal cellular aging process. Immunoblotting of erythrocyte membrane proteins from Alzheimer patients reveals increased breakdown of the anion transport protein band 3 in a majority of the cells, similar to what is observed in only a very small cell population during normal aging. These structural changes are accompanied by changes in anion transport characteristics, but the latter partially deviate from those observed during normal aging. The amount of erythrocyte-bound immunoglobulin G, the most direct and relevant parameter of erythrocyte aging, is significantly increased in Alzheimer patients relative to age-matched, healthy donors and to patients with multi-infarct dementia. These data indicate accelerated molecular breakdown of band 3 and premature appearance of senescent cell characteristics in erythrocytes from Alzheimer patients, and support the hypothesis that abnormal cellular aging may be involved in the etiology of the Alzheimer-specific pathology.