Background: Lichen planus (LP) is an idiopathic papulosquamous disorder, which can show cutaneous or mucosal signs. It is caused by a cell mediated immune response to an antigen. A wide range of clinical manifestations has been reported. Objective: To determine the sex and age frequency and clinical presentations of this disease in patients referred to Razi hospital in Tehran. Patients and Methods: In this observational case series study, patients referred to Razi hospital in Tehran from May to July 2003 were examined and clinically or clinicopathologically confirmed cases of LP were selected. Results: One-hundred and twenty patients had LP (52 females-68 males). The age range was 6-80 years and the mean age was 40.6 years. Sixty-seven of patients had cutaneous lesions, 20% had mucocutaneous and 13% had mucosal lesions. Hypertrophic LP was present in 22% and typical or classic LP was seen in 18%. Seven percent of patients had scalp involvement and oral LP was present in 33.3% of cases and the most common form was reticular. Genital lesions were present in 6% of cases mainly in male cases and as annular form. Six percent of patients had positive family history of LP. Conclusion: In this study LP was more common in male patients and in fourth decade of life. Hypertrophic LP and classic LP were the most common and reticular form was the most common form of oral LP. Genital lesions were mainly seen in male patients and as annular form.