Excessive noise is a global occupational health hazard with considerable social and physiological impacts, including noise-induced hearing loss (NIHL). This paper describes the worldwide morbidity of occupational NIHL in the year 2000. The proportion of the population exposed to occupational noise was estimated using noise exposure data from the US National Institute for Occupational Safety and Health (NIOSH), adjusted by data on the distribution of the work force by occupational category and economic sector, and economic activity rates in each WHO subregion. These values for the exposed population and risk measures for NIHL were used to develop estimates of the attributable fraction (AF) of adult-onset hearing loss resulting from occupational noise exposure. The AFs were applied to WHO estimates of total disability-adjusted life years (DALYs) from adult-onset hearing loss to estimate the DALYs due to occupational noise. Worldwide, 16% of the disabling hearing loss in adults (over 4 million DALYs) is attributed to occupational noise, ranging from 7% to 21% in the various subregions. The effects of the exposure to occupational noise are larger for males than females in all subregions and higher in the developing regions. Occupational noise is a significant cause of adult-onset hearing loss. The majority of this NIHL burden can be minimized by the use of engineering controls to reduce the generation of noise at its source.