summary A large epidemiological health investiga tion, the Helsinki Ageing Study (HAS), was performed in 1989-1991 in Helsinki, Finland. We report here the prevalence of oral mucosal lesions in 338 76-, 81-and 86-year-old home-living elderly people, w ho com pleted the oral health investigation at the Institute of Dentistry, University of Helsinki. One or more lesions were found in 128 subjects (38%). Fifty-one per cent of the edentulous com plete-denture wearers and 31% of the elderly w ith some natural teeth had mucosal lesions* The m ost common finding was inflammation under the denture, w hich occurred alone or combined with other lesions in 25% of the denture wearers. The three m ost common mucosal changes not related to denture wearing were coated changes of the tongue (7%), angular cheilitis (6%) and varicose veins under the tongue (4%). No differences were found in the number of mucosal lesions among the three age groups. Angular cheilitis and inflammation under removable dentures were more frequent in w om en than in men. However, no other differences w ere found in the presence of mucosal lesions betw een sexes. The total number of mucosal lesions correlated J positively with the number of medications used daily. Ninety-six per cent of the subjects w ith complete dentures, and 98% of those w ith som e natural teeth reported cleaning their dentures at least once a day. Of the denture wearers, 88% reported cleaning their oral mucosa also, as part of their oral hygiene routine. The presence of mucosal lesions was related to self-reported cleaning of th e denture-bearing mucosa. However, no association was observed between cleaning frequency and presence of mucosal changes.