The Department of Audiology in Helsinki University Central Hospital provides paedoaudiological services for the Province of Uusimaa, including Helsinki. Our purpose was to study the prevalences of hearing threshold loss in children born in the period 1973 to 1990. The material consisted of 353 hearing-disabled children. The pure-tone average (0.5, 1 and 2 kHz) of the better ear was the parameter for hearing threshold. In 36 subjects the hearing acuity was determined with the behavioural observation test or the brainstem electric response measurement. The number of hearing-impaired per birth year (hearing level > or = 35 dB) ranged from 6 to 30 and the prevalence rate from 0.3 to 1.9 in 1000, totalling 1.1. After matching the hearing-impairment criteria with those of the previous reports from northern Sweden, Denmark and the European Community, we were able to compare the prevalences.