The International Autoimmune Hepatitis Group convened to establish diagnostic criteria for autoimmune hepatitis (AIH). AIH is an autoimmune disorder characterized by chronic liver inflammation, often leading to cirrhosis and high mortality if untreated. It is associated with autoantibodies, a female predominance, and human leukocyte antigens. Previous classifications were insufficient, prompting the need for standardized criteria. The panel reviewed clinical, laboratory, and histological features, noting that current criteria may not apply to all cases. They proposed a scoring system to classify AIH as "definite" or "probable," based on clinical and laboratory findings. Histologically, AIH presents with periportal necrosis and lymphoplasmacytic infiltrates, but these features are also seen in other liver diseases. The panel agreed that lymphoid aggregates and granulomas should not be used to exclude AIH. They also emphasized that AIH should not be subdivided based on autoantibody profiles due to lack of clear therapeutic implications. The panel recommended avoiding the term "chronic persistent hepatitis" and using "minimal" or "mild" disease activity instead. They also discussed overlapping syndromes with other liver diseases, noting that such cases are rare. The panel suggested that patients with biliary changes should not be classified as AIH unless histology confirms it. They emphasized that AIH should be diagnosed based on clinical features, not autoantibody profiles, and that response to therapy should be assessed. The panel also addressed the challenge of distinguishing AIH from non-A, non-B hepatitis, noting that HCV infection is increasingly associated with AIH. They recommended using more reliable diagnostic tests when available. The panel concluded that AIH should be diagnosed based on clinical and laboratory findings, with a scoring system to classify cases as definite or probable. They emphasized that these criteria do not define pathogenic mechanisms or treatment strategies.The International Autoimmune Hepatitis Group convened to establish diagnostic criteria for autoimmune hepatitis (AIH). AIH is an autoimmune disorder characterized by chronic liver inflammation, often leading to cirrhosis and high mortality if untreated. It is associated with autoantibodies, a female predominance, and human leukocyte antigens. Previous classifications were insufficient, prompting the need for standardized criteria. The panel reviewed clinical, laboratory, and histological features, noting that current criteria may not apply to all cases. They proposed a scoring system to classify AIH as "definite" or "probable," based on clinical and laboratory findings. Histologically, AIH presents with periportal necrosis and lymphoplasmacytic infiltrates, but these features are also seen in other liver diseases. The panel agreed that lymphoid aggregates and granulomas should not be used to exclude AIH. They also emphasized that AIH should not be subdivided based on autoantibody profiles due to lack of clear therapeutic implications. The panel recommended avoiding the term "chronic persistent hepatitis" and using "minimal" or "mild" disease activity instead. They also discussed overlapping syndromes with other liver diseases, noting that such cases are rare. The panel suggested that patients with biliary changes should not be classified as AIH unless histology confirms it. They emphasized that AIH should be diagnosed based on clinical features, not autoantibody profiles, and that response to therapy should be assessed. The panel also addressed the challenge of distinguishing AIH from non-A, non-B hepatitis, noting that HCV infection is increasingly associated with AIH. They recommended using more reliable diagnostic tests when available. The panel concluded that AIH should be diagnosed based on clinical and laboratory findings, with a scoring system to classify cases as definite or probable. They emphasized that these criteria do not define pathogenic mechanisms or treatment strategies.