Whereas the histologic findings in clinically "chronic" autoimmune hepatitis have been well established, with piecemeal necrosis as a hallmark lesion, the histologic findings of clinically "acute" or recent-onset autoimmune hepatitis remain undefined. The goal of this study was to define more fully the liver histomorphology in patients with recent-onset autoimmune hepatitis. Twenty-six patients were identified at our institution who had well-characterized autoimmune hepatitis and had undergone a liver biopsy within 6 months of clinical presentation. A detailed histologic evaluation revealed evidence of chronic liver disease in 25 (of 26) patients despite the lack of correlating clinical chronicity. The histologic evidence of chronicity included, in addition to a portal lymphoplasmacytic infiltrate, bridging (septal) fibrosis (11 patients) and overt cirrhosis (four patients). Eighteen of these 25 cases with evidence of chronicity also showed zone 2 and 3 lobular hepatitis, including disarray and hepatocyte necrosis. A single case showed lobular hepatitis with confluent hepatocyte necrosis (submassive hepatocellular necrosis), but no evidence of chronic liver disease. Although autoimmune hepatitis remains in the differential diagnosis of lobular hepatitis, these data show that most patients with autoimmune hepatitis who undergo biopsy early in its clinical course will have histologic evidence of chronic liver disease. Most of these patients probably have a lobular "flare" in disease activity, which likely precipitated the clinical presentation. The findings herein reinforce the concept that autoimmune hepatitis is by definition a chronic disease and supports the proposal that the modifier "chronic" be eliminated from autoimmune hepatitis.