Objective: To investigate the prevalence of oral lichen planus (OLP) lesions in the oral mucosa of adult Turkish dental patients and to determine the association of those lesions with cutaneous lichen planus. Material and Methods: The dental and medical histories were recorded for 5018 patients referred to our institution between June 2004-September 2005 for dental treatment; all patients completed a questionnaire. Clinical examination of each patient was performed. In patients with a mucosal change interpreted as lichen planus by clinical examination, a biopsy specimen was obtained. Patients diagnosed with OLP were examined by a dermatologist to identify cutaneous lichen planus. Results: Fifty-eight (1.15%) patients were diagnosed with OLP after the clinical and histopathological assessment of 5018 patients. There was no gender-related difference in the incidence of OLP (p > 0.05) according to the Chi-square test. Eleven patients showed signs characteristic of cutaneous lichen lesions. Seven oral lichenoid lesions were attributed to lichenoid reaction. The lesions were most common on the buccal mucosa. The most prevalent type was the reticular. Histopathological examination of the specimens obtained from 4 patients with OLP showed epithelial dysplasia. Conclusion: Clinicians must be vigilant in assessing patients for the signs of OLP because of its relatively high dysplastic potential.