Autoimmune Hepatitis (AIH) is chronic fibroinflammatory disease of the liver characterized by chronic, relapsing liver inflammation, and a risk for progression to liver failure and need for liver transplantation. No AIH-specific registry does exist in Italy, so that the actual epidemiology of the disease in the country is unknown. This is an observational, retrospective and prospective, multicenter study evaluating incidence, prevalence and disease course of AIH in subjects \> 1 years old in Italy.