40Hz event related potential(40Hz ERP) described by Galambos in 1981 has been considered as the useful potential in predicting hearing threshold across the audiometric frequencies. Estimates of hearing threshold using the 40Hz ERP were obtained on 197 hearing impaired subjects at frequencies of 500, 1000, 2000Hz and compared with pure tone audiometry. The results were as following ; 1) The mean difference were within 13dB at 500Hz, 15dB at 1000Hz, 22dB at 2000Hz. 2) Regardless of hearing loss type, the mean amplitude was decreased as stimulus frequency increased. 3) Regardless of hearing loss type, peak latency increased as stimulus frequency decreased. 4) Within 5dB agreement between 40Hz ERP and pure tone averages(PTA) in the cases of severe hearing impaired subjects(especially 60dB or poorer).