Hepatic vein (HV) thrombosis causes ascites, hepatomegaly, and severe congestion of the liver (Budd-Chiari syndrome [BCS]). Severe hepatic fibrosis develops in this syndrome with a variety of histological patterns. Some livers have a pattern of cirrhosis in which there is fibrous bridging between HVs and portal tracts (veno-portal cirrhosis). Other livers have a pattern of "reversed-lobulation cirrhosis" (veno-centric cirrhosis), in which fibrous bridging between HVs and portal tracts is minimal. The prevalence and pathogenesis of these forms of cirrhosis and the effect of portal vein (PV) thrombosis in this disease have not been studied. We examined 15 resected livers from patients with BCS to determine the distribution of vascular obstruction and the character of the parenchymal response. Six livers had veno-portal cirrhosis, and all of these had severe PV obliteration caused by thrombosis. Three livers had veno-centric cirrhosis and had normal medium and large PVs. The remaining six livers had mixed veno-centric/veno-portal cirrhosis and had moderate PV obliteration. The nodules in veno-centric cirrhosis had evidence of an unusual circulation with small arteries supplying a midzonal venous plexus that appeared to drain retrogradely into patent small PVs. Nine livers had large regenerative nodules histologically similar to focal nodular hyperplasia. PV thrombosis is a frequent occurrence in BCS. The correlation between PV thrombosis and the pattern of cirrhosis suggests a role for PV obliteration in the genesis of veno-portal bridging fibrosis in this disease and possibly in other diseases leading to cirrhosis.