It is very difficult to distinguish between occupational noise-induced hearing loss and other diseases with cochlear hearing loss by the means of conventional audiometric tests. Otoacoustic emission measurement is a relatively new tool for assessing the inner ear function. It gives an opportunity of monitoring the status of the outer hair cells, the elements which are the most sensitive to noise-induced damage. In this study the results of distortion product otoacoustic emission (DPOAE) measurement in subjects with industrial noise-induced hearing loss, presbycusis and hearing impairment caused by gentamycin, are presented. In all these cases pure-tone audiometry revealed similar shape of the audiograms with cochlear hearing loss mainly at high frequencies. In the cases of industrial noise-induced hearing loss, DPOAE measurements demonstrated a very typical shape of DP-gram with the decrease (notch) in otoacoustic primarily at the frequencies of 3-4 kHz. Such a notch in DP-grams was not observed in the cochlear hearing loss caused by factors other than noise. The data indicate that otoacoustic emissions may be useful in the differential diagnosis of occupational noise-induced hearing loss.