Background: Study the effect of traffic noise on hearing ability of police offcers. Method: Sixty male and 15 female traffic police officers were chosen. All of the officers chosen are under 30 years of age and have no previous history of otological diseases. Result: Among the male officers who have worked for three years or less in Taipei, 16.7% are likely to have noiseinduced hearing loss, while 23.3% of the male officers worked for over three years in Taipei developed hearing loss. Between male officers who worked for less than 3 years and the ones who worked for over 3 years, there is a significant difference in the average pure tone hearing threshold above 3000 Hz. For all the female police officers, the hearing threshold in all frequencies are below 25 dB HL. Conclusions: The longer the male traffic police officers work in Taipei, the worse their hearing ability are.