An excitatory potential generated in response to stimulation by a current pulse has been studied on an artificial membrane composed of a Nuclepore filter impregnated with sorbitan monooleate. An excitatory potential response accompanying a fall in the resistance of the membrane was found to occur above a threshold value of the pulse height for current stimulation. The relation between the pulse width of current stimulation and the threshold for the generation of an excitatory potential response has also been examined.