Abstract: Deep tendon reflexes, plantar responses, muscle tone and release signs were studied as 14 individual clinical variables and as 5 summary variables in 135 aged subjects, including 27 controls, 20 subjects with mild cognitive impairment, and 88 subjects with successive stages of probable Alzheimer's disease (AD). Changes in activity of elicited responses were rated on a seven-point scale. Results were analyzed both as prevalence and mean degree of change in activity. Mild cognitive impairment was associated with a significantly higher rating than controls on a variable combining all 14 individual variables. Subjects with early AD had both higher prevalence of increased activity and increased mean scores of deep tendon reflexes and muscle tone. They had a higher prevalence of increased activity on a variable combining three release signs. Patients with late stage AD had significantly increased prevalence and mean scores of muscle tone, grasping and sucking reflexes compared with controls and early AD patients.