The goal of the proposed research is to understand developmental aspects of ototoxicity in order to prevent this form of aquired hearning loss, and to apply this information to normal auditory development. The rationale for this work is based upon the demonstration of a susceptible developmental period in multiple animal models, using a variety cochlear implants including accoustic trauma, aminoglycosides, and loop diuretics. Exposure to ototoxic agents before and after this period reults in less severe auditory dysfunction.