Our previous studies of stimulated oto-acoustic emissions (OAEs) have revealed that the OAE threshold indicates the grade of inner ear impairment. The present study is a survey of OAE in children of school age. The mean OAE threshold values of 113 ears with normal hearing and 45 ears with functional deafness were 5.9 dB nHL and 6.2 dB nHL, respectively. In sensorineural loss the value was noted to increase according to its grade, classified into four groups, measuring 37.2 dB nHL in the group with severe loss higher than 91 dB. The findings suggest that the OAE threshold is useful for an indicator of inner ear function in children. There still remains the problem to be solved by a contrivance of noise removal for application of OAE to hearing tests in children of pre-school age.