A data bank of prevalence of hearing impairment for monitoring and implementation of programmes at national or global level and for the estimate of the global burden has been established. A systematic search was conducted of random-sample population-based studies of bilateral hearing impairment with clearly defined hearing threshold levels. Fifty-three studies from 31 countries from all WHO regions were found to meet the selection criteria. The prevalence of mild and disabling hearing impairment and other details from the studies are reported by WHO region. Although a large number of studies were found, only a small number among them were suitable surveys of prevalence of bilateral hearing impairment in the general population. Hearing impairment is a major disability that should be monitored at all ages: more population-based surveys are needed in all regions of the world. Utilization of the WHO protocol is recommended for collection and analysis of data in standard ways; especially recommended is the use of WHO threshold levels and to report the prevalence of bilateral impairment, both of which required to calculate burden.