Lesions of the oral mucosa associated with wearing of removable dentures may represent acute or chronic reactions to microbial denture plaque, a reaction to constituents of the denture base material, or a mechanical denture injury. The lesions constitute a heterogeneous group with regard to pathogenesis. They include denture stomatitis, angular cheilitis, traumatic ulcers, denture irritation hyperplasia, flabby ridges, and oral carcinomas. Denture stomatitis is the most common condition which affects the palatal mucosa in about 50% of wearers of complete or partial removable dentures. Most of the lesions caused by chronic infection (Candida albicans) or mechanical injury whereas allergic reactions to the denture base materials are uncommon. Angular cheilitis (lesions of the angles of the mouth) is characterized by maceration, erythema and crust formation. The prevalence is about 15% among wearers of complete dentures. The lesions have an infectious origin but several local, including prosthetic, or systemic predisposing conditions are usually present. Traumatic ulcers caused by dentures with overextended or unbalanced occlusion are seen in about 5% of denture wearers. Denture irritation hyperplasia, which is caused by chronic injury of the tissue in contact with the denture border, is present in about 12% of denture wearers. Flabby ridge, which is replacement of alveolar bone by fibrous tissue, is present in 10-20%. Finally, there is evidence that chronic injury of the oral mucosa by dentures in rare instances may predispose to development of carcinomas. Most types of lesions are benign and quite symptomless. However, diagnosis may be difficult and the more severe and dramatic tissue reactions to dentures may indicate underlying systemic diseases. In order to prevent or minimize the extent of the lesions, denture wearers should be recalled regularly for an examination of the oral cavity and the dentures. It is important that the examination is carried out by a person who has adequate medical knowledge.