National surveys of alcoholic liver disease (ALD) in Japan were performed in 1978 and 1985 by a previous Japanese study group for ALD (the Takeuchi group). In the present study, a subsequent nationwide survey of ALD in Japan was conducted from 1986 to 1991 and the results compared with the previous studies. In order to clarify the aetiological relationship between hepatitis C virus (HCV) infection and ALD, results were also analysed according to new diagnostic criteria for ALD proposed by the current ALD study group (the Takada group). According to the diagnostic criteria of the Takeuchi group, the incidence of ALD did not differ significantly from 1986 to 1991. However, the incidence of hepatocellular carcinoma (HCC) in alcoholic cirrhosis (AL-LC) clearly increased during this period. The analysis, which included analysis of results from the previous studies, indicated that the incidence of ALD reached a plateau in 1980 and then stabilized. However, HCC in AL-LC continued to show a linear increase from 1976 to 1991. The new diagnostic criteria of the Takada group were used to analyse cases from 1990 and 1991. Approximately two out of every three cases of ALD were caused by alcohol alone, and the remainder were caused by a combination of alcohol and HCV. Cases caused only by HCV were very rare. The main aetiology in patients with alcoholic hepatitis and fibrosis was alcohol alone, and in the case of chronic hepatitis, in heavy drinkers, it was a combination of alcohol and HCV. In half the patients with AL-LC the aetiology was alcohol alone, and in the other half it was a combination of both alcohol and HCV. In the majority of patients with HCC, the aetiology was a combination of alcohol and HCV, indicating that HCV infection may be important in the development of HCC in alcoholics.