Slowing of the deep tendon reflexes has been recognized for many years as a characteristic phenomenon of untreated myxedema.1 On palpation of the tendon during reflex motion the slowness of response is particularly apparent in the relaxation phase, and "delayed relaxation" is a useful diagnostic sign of myxedema, since it does not appear with any regularity in any other disease. The biceps brachii and the Achilles tendon reflexes are most convenient for this demonstration. Lambert and co-workers2 were able to record by means of special apparatus the mechanical events of the ankle jerk in myxedema and other metabolic abnormalities. Both contraction and relaxation were significantly prolonged, the latter often markedly so, and beyond the range of normal in 77% of patients with myxedema. In contrast, all patients with low basal metabolic rates but without myxedema showed normal reflex patterns. All myxedematous patients, including those whose initial reflex time