Difficulty in assessment of potentiating interaction between noise-induced and kanamycin-induced injury of hearing is compounded by the great variability of intersubject response to the same drug dosage. However, in a given subject, response of the two cochleas to kanamycin intoxication may resonably be assumed to be symmetric. The present study was designed to utilize this similarity, in determining whether kanamycin intoxication would potentiate a normally subtraumatic noise stimulus. Under the experimental conditions outlined, it was found that after a dosage of 150 mg/kg/day of kanamycin given to a physiologic end point, normally subtraumatic noise caused consistent increas in hearing loss.