This study determined the prevalence of oral mucosal alterations and associated factors among the institutionalized elderly in Brazil. Data were collected through a structured questionnaire, a review of their medical records and an intra-oral examination. A sample of 335 individuals over 60 years of age was randomly selected. In total, 646 alterations were diagnosed; 59.1% were variations of the normal oral mucosa. The most frequent variation consisted of sublingual varicosities (51.6%). Denture stomatitis (15.2%) and denture hyperplasia (12.8%) were the most frequent lesions. Elderly patients who wore dentures had a significantly higher prevalence of oral mucosal lesions (p = 0.00) than those that didn't wear dentures. There was a high prevalence of variations of the normal oral mucosa and of mucosal lesions, especially denture-induced lesions, among the institutionalized elderly.