A group of 192 firefighters serving in a busy urban emergency medical services (EMS) system was randomly selected for hearing tests. Total number of hours of siren noise exposure was calculated for each man and was compared to the outcome of hearing tests. Hearing loss was defined by the amount of sound intensity required to sense both midfrequency and high-frequency tones. Results indicated a correlation between hearing loss and the duration of siren noise exposure. The loss could not be attributed to non-job-related sources. In addition, the rate of hearing loss over time was 150% of that expected in age-matched, non-noise-exposed men. These findings confirm the observations of others that EMS personnel are at risk for hearing loss beyond that expected from aging alone, and they document that the hearing loss correlates with the duration of intense siren noise exposure.