There were an estimated 10 million new cases, 6 million deaths and 22 million persons living with cancer in the year 2000. The most common cancers are, in terms of new cases, lung (1.2 million), breast (1.05 million), colon-rectum (945 000), stomach (876 000) and liver (564 000). The geographic distributions of some 20 types of cancer for which national estimates have been made are summarized. These patterns are examined with respect to the likely reasons in terms of variation in exposure to carcinogens (in the external environment or through lifestyle choices) or in genetic susceptibility to them. Related data from studies of migrant populations (that allow comparisons of genetically similar populations living in different environments) and from comparisons between different ethnic groups living in the same country are used to help in the interpretation of the geographic patterns. Information on the burden of disease also has a very important role in the planning and monitoring of programmes of cancer control.