Autoimmune hepatitis (AIH) is a hepatocellular inflammation that is characterised by a wide range of histopathologic (periportal interface hepatitis with plasma cell infiltration and piecemeal necrosis), biochemical (hypertransaminasemia, hypergammaglobulinaemia) and autoimmune (several autoantibodies presence) features. This relatively rare disorder frequently affects middle-aged women. There is no pathognomonic marker for AIH diagnosis, therefore it requires a careful rule out of other causes of liver disease together with the detection of a suggestive pattern of clinical and laboratory abnormalities. Scoring system for AIH diagnosis proposed by International Autoimmune Hepatitis Group has been used as a tool in clinical practice but is not sufficiently exclusive in terms of defining prognosis or treatment. AIH has been classified in two subtypes according to autoantibodies detected: 1 and 2, but this classification results in poor clinical implications. Previously known as subtype 3 is at the present included in subtype 1 because no clinical significant differences has been found between them. Aetiology, and molecular mechanisms still remain to be elucitaded in this disease, although viruses, drugs and molecular mimicry act presumably as a trigger in genetically predisposed patients (associated with HLA-DR3 and DR4 haplotypes). On the other hand, immunosuppressive therapy (corticosteroid or azathioprine) generally offers favourable response. Our aim is to review this disease from different points of view, considering: clinical, histopathological, etiologic, genetic, biochemical, autoimmune, treatment and prognosis features.