Hepatocellular carcinoma is closely associated with cirrhosis, but it also develops, although much less frequently, in a noncirrhotic liver. It is suspected, without supporting evidence, that hepatocellular carcinoma has a different etiology when associated and not associated with chronic liver disease. In this study, 66 noncirrhotic cases found among 618 autopsies for hepatocellular carcinoma (10.7%) were analyzed retrospectively. The noncirrhotic liver was histologically unremarkable in 3 cases and in the histologically evaluable 56 cases it had fibrosis of varying degrees or mild cellular infiltrate, or both, in the portal tract. There was one liver that had portal venous changes compatible with those in idiopathic portal hypertension (Banti's syndrome). In these noncirrhotic livers, the parenchymal cells were generally unremarkable except for liver cell dysplasia that was seen in 26.8%. Serum hepatitis B surface antigen was positive in only 7.4% in contrast to 26.6% in cirrhotic cases. Three histologically unremarkable cases had no clinical or histologic evidence of chronic liver disease; two involved painter-plasterers and one a farmer. The liver weight in these cases ranged from 4400 to 6180 g. In contrast, the average liver weight in cirrhotic cases was 1998 g. Noncirrhotic patients when compared with cirrhotic patients had better liver function tests and much less frequent varices. It was concluded that approximately 11% of hepatocellular carcinoma cases in Japan are noncirrhotic, the majority having some histologic changes in the portal tracts suggestive of past or ongoing chronic liver disease, and that there are rare cases that have no histologic changes in the liver.