We examined 41 consecutive cirrhotic liver explants from French patients for the presence of nodules of adenomatous hyperplasia (AH) and then analyzed these lesions, together with underlying cirrhosis (C) and associated hepatocellular carcinoma (HCC), for various histological parameters, cellular density, and proliferative activity. Thirty-five AHs were identified in 10 livers (prevalence, 24%); seven of 10 were HCV positive. Hepatocellular carcinoma was more frequent in patients with AH than in patients without. The AHs consisted of 17 ordinary (OAH) and 18 atypical (AAH) adenomatous hyperplasia lesions. There was a malignant focus in five of the 18 AAHs. Wide areas of large liver cell dysplasia were frequent in OAH but never found in AAH. Obvious steatosis was frequent in HCC but exceptional in AAH and absent in OAH. There was a significant increase in cellular density in AAH and HCC as compared with C and OAH. Proliferative cell nuclear antigen immunostaining similarly showed an increase in proliferation from OAH or C to AAH and HCC. These data suggest that, in Europe as in Japan, one pathway of hepatocarcinogenesis is a multistep process in which AAH should be considered as a premalignant lesion very close to grade I HCC, while OAH seems to correspond to a regenerative nodule with limited proliferative ability.