The present study deals with the auditory sensitivity of men and women 40 to 64 years of age living in two municipalities situated in the southwestern part of Finland and the prevalence of defective hearing in this middle-aged population. Hearing acuity was tested in 1043 men (93.2%) and 1221 women (93.1%). It appeared in the investigation that hearing loss increased markedly with age in both sexes. Auditory sensitivity was clearly better in women than in men. Of the entire population 7.1% had evident bilateral hearing loss when an average loss of 25 dB in the speech range was used as the cut-off point. Hearing loss of 35 dB in the speech area was regarded as requiring an otological examination and possible care even when present in only one ear. Of the men 12.1% and 7.9% of the women were in this category; this represents an overall prevalence of 9.9%.