A long-term cohort study of 639 males in a farming area and 677 males in a fishing area in Kyushu, Japan, has been conducted to evaluate risk factors for ischemic heart disease. The present investigation utilized this long-term cohort study to assess the role of drinking and cigarette smoking habits in the causation of liver cancer. The O/E ratio (ratio of the observed to expected number of deaths) of liver cancer was 7.5 (P less than 0.001) among shochu drinkers in the fishing area. Further, a clear dose-response relationship of O/E ratio was noted: 5.7 (P less than 0.001), 7.5 (P less than 0.001) and 20.0 (P less than 0.001) for drinkers of less than 1, 1-2, and 2 or more units of shochu (a distilled alcoholic beverage made in Japan; about 25% alcohol). Although no excess risk was found among shochu drinkers in the farming area, observed and expected numbers were too small to make valid judgements. Among sake drinkers, the observed and expected numbers were very similar in both areas. Cigarette smokers in the fishing area appeared to have a high risk for liver cancer, the O/E ratio being 4.8 (P less than 0.001). However, there was no clear dose-response relationship and O/E ratios among cigarette smokers according to their drinking habits indicated no excess risk among nondrinkers. A multiple logistic regression analysis showed an insignificant effect of cigarette smoking on the development of liver cancer after adjustment for shochu drinking. These findings suggest a significant involvement of shochu drinking in the etiology of liver cancer, at least in this fishing area.