40Hz event related potentials(ERP) in response to 0.5KHz, 1KHz and 2KHz tone pips were obtained in order to assess their reliability and thresholds in normal and hearing loss patients. They were compared with pure tone thresholds. In normal group, 40Hz ERP was almost all detected within 20dB HL in various frequencies and their latencies were decreased with increasing stimulus intensities. In hearing loss group, the mean differences between 40Hz ERP thresholds and pure tone thresholds were within 25dB. There were 30 differences between conductive and SNHL cases. The correlation coefficients between 40Hz ERP thresholds and pure tone thresholds were from 0.81 to 0.87. These results shows that the 40Hz ERP is a useful tool for determining accurate hearing threshold.