A survey is made of comparative studies of ototoxicity of different aminoglycoside antibiotics. Animal studies show clearly lower netilmicin ototoxicity compared with that of other aminoglycoside antibiotics. Clinical controlled comparative trials are few. Most studies have few patients in each group. The significance of auditory threshold shifts in single frequencies as criteria of ototoxicity is uncertain. An analysis of clinical and animal studies together indicates, however, that netilmicin has a higher ratio of efficacy to ototoxicity than other aminoglycoside antibiotics.