Percutaneous transhepatic portal vein embolization (PTPE) produces regenerative hypertrophy in the nonembolized part of the liver, but the regenerative capacity after PTPE in patients with chronic hepatitis is unknown. We studied 34 patients with hepatocellular carcinoma and chronic hepatitis who underwent PTPE at the right portal vein. Hepatic lobular volumes were calculated by computed tomography before and 2 weeks after PTPE. The increase in left lobular volume was analyzed using a stepwise multiple regression method incorporating 11 factors: age; portal venous pressure; proportional volume of the right lobe; indocyanine green retention test; platelet count; serum levels of aspartate transaminase, alanine transaminase, total bilirubin, and albumin; and histological inflammatory grade and stage of fibrosis, according to the criteria of the International Association for the Study of the Liver recommended at their 1994 meeting. The median volume of the left lobe had increased from 405 to 554 cm3 (P < 0.0001) by 2 weeks after PTPE. Inflammatory grade was the only independent factor predicting regenerative hypertrophy (regeneration ratio (%) = 80.3 - 20.1 x grade; standard correlation coefficient = -0.566; P = 0.0014). Histological inflammatory activity was the essential factor regulating liver regeneration after PTPE in patients with chronic hepatitis.