Some clinical methods of differential diagnosis for recruitment phenomenon have already been investigated by some authors. The SISI test which was a test for differential intensity sensitivity was introduced by Jerger et al. in 1959 and it was taken as a clinical method in many countries. In present study, an observation on SISI test for 190 ears of 100 cases, including both normal hearing and impaired hearing groups was performed and following results were obtained. 1) Normal hearing group (30 ears of 15 cases) showed entirely 0% except one ear. 2) Conductive hearing loss group (64 ears of 33 cases) showed negative score(0-20%) in 62 ears except two ears. 3) In mixed hearing loss group (39 ears of 23 cases) 4 ears presented positive score (60-100%) and 35 ears were 50% or lower in SISI score. 4) In sensori-neural hearing loss group(57 ears of 29 cases), 38 ears were negative, 13 ears were positive and 6 ears showed questionable score(25-55%).