A comparative, descriptive study on the prevalence of hepatocellular carcinoma either associated or not with cirrhosis was undertaken between the cities of Trieste, Italy, and Chiba, Japan. Data were derived from 12,340 and 2,052 autopsies consecutively performed in Trieste and Chiba during 1980 to 1984 and 1975 to 1985, respectively. During these years, more than 70% of all deaths were studied by autopsy in Trieste. Clinical cases of hepatocellular carcinoma admitted to the Chiba University Hospital were also analyzed to correct for the bias induced by the relatively small number of autopsies in Chiba. Serum hepatitis B surface antigen was more frequent in Chiba, whereas alcohol intake was greater in Trieste. From the comparison of the data, we conclude: (i) hepatocellular carcinoma was associated with cirrhosis in the large majority of the cases both in Trieste (87%) and Chiba (81%); (ii) in both sexes, the average age of hepatocellular carcinoma patients was significantly older (p less than 0.005) in Trieste than in Chiba; (iii) in the autopsy series, cirrhosis was more frequent in Trieste (9.7%) than in Chiba (1.5%); (iv) in Chiba, hepatocellular carcinoma was more frequent than cirrhosis not complicated by hepatocellular carcinoma (6.9 vs. 1.5%) at necroscopy, and (v) the age-standardized rate of hepatocellular carcinoma was significantly (p less than 0.01) higher in Trieste than in Chiba. These geographical differences might be related to the different type of cirrhosis observed in Trieste (alcoholic) and Chiba (postnecrotic).