Similarities were noted between the nature of inner ear damage produced by loud sounds and by aminoglycoside antibiotics. Since body temperature affects cochlear function and influences the effects of noise on the ear, a similar effect was predicted for the aminoglycoside, kanamycin. By environmentally elevating the body temperatures of preweanling mice to approximately 1C above that of the normal adult, kanamycin ototoxicity was increased (an average 20.4 dB threshold elevation, vs. 9.3 dB for kanamycin injected mice reared at room temperature). Hyperthermia per se had no influence on auditory thresholds. This may be of relevance to humans with fever who are treated with aminoglycoside antibiotics.