A trend in the incidence of hepatocellular carcinoma (HCC) in Japan was studied from the data of the Osaka Cancer Registry (population, 8,512,351 in 1981) for the period of 1963–1983, the Vital Statistics of Japan, Ministry of Health and Welfare, and the Japan Autopsy Registry which contained 594,132 individually filed cases in the 26-year period from 1958 to 1983. Both cancer registry data and autopsy records showed a more than 2-fold increase in HCC incidence, particularly in the last 10 years or so, among males and a less pronounced increase in females. The same trend was borne out by the cancer registries of Nagasaki City and Miyagi Prefecture and the Vital Statistics. When studied with the autopsy data, it was found that the numbers of autopsies for cirrhosis without HCC and autopsies for HCC (with and without cirrhosis) were about the same in 1958–1961 and that currently (1980–1983) the latter is about 2 times the former. As one of the possible causes of increase in HCC incidence other than prolonged survival of patients with cirrhosis, chronic non-A, non-B hepatitis is discussed.