A series of investigations into the sensitization of the auditory and tactile systems by prior stimulation is reported. Two apparently different types of sensitization were found: (1) A “sustained” type that was elicited following exposure to low‐intensity sitmulation and which may be related to the density of functional receptor elements in the region stimulated; (2) A “transitory” type that required exposure to moderately intense stimulation and which apparently occurred only when two regions of differing sensitivity were stimulated simultaneously. In the auditory system, “sustained” sensitization appeared in both the ipsilateral and contralateral ears, “transitory” sensitization occurred only in the ipsilateral ear.