Based on a population-based cancer registry in Khon Kaen Province, Thailand, data were collected actively and passively from all hospitals, health centers and the office of the Chief Medical Officer of Khon Kaen. The data were collected prospectively for the year 1988 and retrospectively for the years 1985-1987. Liver cancer, especially cholangiocarcinoma, was the leading cancer in both sexes. The age-standardized incidence rates for the year 1988 were 89.2/10(5) in males and 35.5/10(5) in females respectively, which are among the highest rates recorded in the world. The number of reported liver cancer cases increased each year. The observed geographical clusters of liver cancer appear to be associated with the prevalence and intensity of Opisthorchis viverrini infection, as reported in previous studies in this area.