Autoimmune hepatitis (AIH) is a generally progressive, chronic liver disease of unknown etiology, relatively uncommon, associated with chronic hepatic inflammation. An environmental agent is hypothesized to trigger an immune-mediated attack directed against liver antigens in genetically predisposed individuals. The disease can lead to potentially fatal liver dysfunction. AIH is characterized by female predominance (sex ratio 3.6:1), hypergammaglobulinemia, circulating autoantibodies and association with human leukocyte antigens DR3 or DR4. The diagnosis of AIH is based on the revised descriptive criteria reported by the International Autoimmune Hepatitis Group in 1999. Without appropriate immunosuppressive therapy AIH has a very poor prognosis with 10-year survival rates as low as 10%, but usually very good response to immunosuppression, and survival rates of responders to the treatment are similar to those of healthy counterparts from the same population.