Autoimmune hepatitis (AIH) is a generally progressive inflammatory liver disease of unknown etiology that occurs in adults and children. Although the peak age of incidence is in prepubertal girls, AIH has been diagnosed as early 6 months of age. Two types of AIH are recognized according to the nature of the autoantibody detected in children at the time of diagnosis. The diagnosis of AIH is based on histological abnormalities, characteristic clinical and biochemical findings, and abnormal levels of serum globulin due almost exclusively to markedly increased immunoglobulin G including various autoantibodies. A genetic predisposition is suggested by the increase frequency of human leukocyte antigen (HLA) haplotypes HLA-B8/DR3, and allotypes DR3 and DR4. However, the incidence of these HLA types is different in each country.Proposed triggers of AIH that may initiate the inflammatory process include some viral infections and some drugs. There is much information about adults with AIH, however, little information on AIH in children, especially in Japanese children. To clarify the clinicohistological features of AIH in Japanese children, we analyzed the clinical, pathological features and response to treatment in 12 Japanese children with AIH. Furthermore, we discuss several problems for diagnosis and treatment for AIH in children.