In order to determine the incidence and the pathological significance of absent tendon reflexes in old age, the tendon reflexes were obtained in 100 persons below the age of 75. Beyond this age, however, absence of certain reflexes was demonstrated with considerable frequency. Thus the ankle jerks were missing in one third of the cases. No correlation could be demonstrated between absence of tendon reflexes and presence of anaemia or diabetes mellitus. The implications of these findings in relation to the clinical diagnosis of diabetic neuropathy in the elderly are discussed. It is suggested that the disappearance of tendon reflexes in old age is a manifestation of a peripheral neuropathy caused by arteriosclerotic obstruction of the vasa nervorum.