Recent evidences of a predisposing genetic factor associated with Alzheimer's disease (DAT) suggests that important alterations may be expressed in tissues other than the brain. We present morphological and biochemical studies on muscle obtained from ten patients with Alzheimer's disease and coeval controls. Muscle biopsy examination showed an increased subsarcolemmal mitochondrial oxidative activity in three patients. The biochemical studies showed an increased oxidative enzyme activity only in the DAT group. The CoQ10 level, studied so far in three DAT patients, was greatly reduced (approximately 50%) compared with controls. Possible new peripheral markers in Alzheimer's disease will be discussed.