Aim: To determine the causes of cirrhosis in Iranian population, and defining the common aetiologies according to patients' sex and age groups. Patients and Methods: 170 patients who were referred to a referral digestive disease centre (Shariati hospital) since 1994-1998 enrolled to a prospective study. All patients had histological and/or clinical and para clinical findings compatible with cirrhosis. Majority of them had complete assessment of history and physical exam oriented for liver disease, liver function tests, abdominal ultrasound and viral serology.Results: Frequency of the causes of liver cirrhosis in our patients (112 M, 58 F, between 7 to 75 years, mean age 44 ± 17.2) were as follow: viral hepatitis type B in 103 patients (60.6%) was the most common cause of cirrhosis, Wilson's disease found in 15 cases (8.8%), autoimmune hepatitis in 14 cases (8.2%), alcoholic liver disease in 6 cases (3.5%), Budd-Chiari syndrome in 6 cases (3.5%), hepatitis C virus infection in 6 cases (3.5%), primary biliary cirrhosis in 2 cases (1.2%); secondary biliary cirrhosis; and confection of HBV and HCV each with 3 cases (1.8%). In 10 patients (5.9%) aetiology of cirrhosis remained unknown.Conclusion: Viral hepatitis B is the most common cause of cirrhosis in Iran. Co-infection of HBV and\HCV is rare. The other causes of liver cirrhosis were Wilson's disease, autoimmune hepatitis, alcoholic liver disease, Budd- Chiari syndrome and hepatitis C infection, respectively. Wilson's disease was the most common cause of cirrhosis in patients less than twenty years of age. Apart from HBV infection that was the most common cause of cirrhosis in both genders, the second aetiology in male patients was Wilson's disease and in female patients was autoimmune hepatitis.