The incidence of the two principle types of liver cancer (hepatocellular carcinoma and cholangiocarcinoma) in five different areas of Thailand was compared with the prevalence of exposure to the main risk factors in samples of the population. Cholangiocarcinoma showed striking variations in incidence, which correlated closely with markers of exposure to the liver fluke, Opisthorchis viverrini. However, there was little geographic variation in incidence of hepatocellular carcinoma or in prevalence of the major risk factors (chronic carriage of hepatitis B virus and exposure to aflatoxin), and apparently there was little relationship between them.