Autoimmune hepatitis, a chronic necroinflammatory disorder of unknown etiology, is characterized by immunologic and autoimmunologic features. It is more prevalent in women than in men, and genetic factors appear to play a major role in the disease. The classification of autoimmune hepatitis is based on circulating autoantibody status; however, heterogeneity is distinguished not only by autoantibodies, but by histologic differences, a variety of clinical features, immunogenetic status, and probably pathogenesis. Presentation extends from the asymptomatic to the severely ill patient. Although patients may present with or without evidence of circulating autoantibodies, hyperglobulinemia is a rather consistent laboratory feature. Because the disease is generally steroid-responsive, therapeutic remission rates of 60-80% have been achieved with prednisone or a combination of prednisone and azathioprine, and many patients can be maintained with these drugs alone or in combination. There are no firm guidelines for decisions regarding withdrawal or reduction of medication. When treatment failures occur, orthotopic liver transplantation may be required.