Abstract Objectives: The purpose of this study was to assess the prevalence and distribution of oral mucosal lesions in a Turkish adult population.Material and methods: Five thousand consecutive patients were examined during routine dental treatment. Some of the mucosal changes were diagnosed solely by clinical examination. When clinical features were not diagnostic, a biopsy was undertaken. Chi-square test was used to analyze the data.Results: The overall incidence of oral mucosal changes or lesions was 15.5%. The lesions were classifi ed as anatomic changes, ulcerated lesions, tongue lesions, white lesions, benign lesions, color alterations, and malignant lesions. Anatomic changes (7%), ulcerated lesions (6.6%), and tongue lesions (4.6%) were the most common lesions.White lesions were observed in 2.2% of all patients. Among the white lesions, leukoplakia was identifi ed in men 4 times more frequently than it was in women. Benign lesions and color alterations were identifi ed in 1.6% and 1.2% of all patients, respectively. In addition, 3 patients (0.06%) were diagnosed as having squamous cell carcinoma, and 1 patient (0.02%) was diagnosed as having adenocarcinoma. There was a statistically signifi cant relation between smoking and the occurrence of mucosal lesions whereas no relation was found between alcohol consumption and mucosal lesion occurrence. Besides, no relation was found between systemic diseases and oral mucosal lesion occurrence.Conclusions: This study has provided information about the epidemiologic aspects of oral mucosal lesions that may prove valuable in planning of future oral health studies.