An audiometric study was carried out in a community of 642 subjects severely affected by endemic goitre and cretinism. Hearing loss was measured in 34 out of 41 subjects diagnosed as cretins, 92 normal subjects aged 5–20 years from the same community and 54 subjects (also of 5–20 years) living in a nearby control area without endemic goitre. The excess number of hearing defects in the endemic area seems to be entirely due to the process that leads to cretinism. There is no reason to describe deafness and deafmutism in an area with severe endemic goitre as a separate entity. The hearing defect showed a definite greater loss in the higher frequencies than in the lower frequencies and was found in 92 % of the cretins. Deafmutism was present in 5, a loss of more than 60 db in 8, a loss of 40–60 db in 10 cretins. A loss of 20–30 db was found in 2.2 % of normal subjects in the endemic area and 1.8 % of those living in the control area. It is concluded that audiometry is a simple and significant test to establish the presence of the neurological form of endemic cretinism, which is the most prevalent form in most endemias. The differential diagnosis and pathogenesis of the described hearing defect are discussed.