Sciatic nerves isolated from Rana pipiens or R. catesbiana and painted with or soaked in solns. of yohimbine HCl (1/100,000-1/5000), strychnine SO4 (1/50,000-1/10,000), quinine HCl (1/5000-1/1000) or one of various local anesthetics were used in a cathode ray oscillograph study of the recovery of excitability after response. After a single stimulation, they manifested not only the familiar refractory and supernormal periods, but also a subsequent period of subnormal excitability, first visible at the end of the supernormal period, but gradually encroaching on the latter and eventually becoming continuous with the prolonged refractory period. The max. degree of subnormality after a single shock was 0.5-30% of the resting level of irritability, occurred 0.1-3 secs. after the shock, and lasted 1-30 sec. Yohimbine induces more prolonged subnormality than do the other poisons. During the subnormal period the max. height of response is unchanged, but the conduction rate is decreased. The subnormality of conduction rate is less than that of excitability. Repeated stimulation at intervals not exceeding the duration of the subnormal period increases the degree and duration of the subnormality. The poisons inducing the manifestation of subnormality tend to depress the spike height, the conduction rate, and (except strychnine) the resting excitability. Subnormality is not identical with refractoriness, but the process associated with it probably begins very early in nerve response. This process, which may actually be a complex of processes, is regarded as a normal constituent of the recovery of nerve.