The distribution of cancers of the lung and stomach in the counties of England and Wales in 1968-81 was mapped, and compared to the distribution in the country in 1921-30 described by Stocks. The high risk of stomach cancer in North Wales noted by Stocks was found still to exist in each sex, although its disparity from the rest of the country has diminished. In general the geographic distribution of stomach cancer in both periods has paralleled that of post-neonatal mortality, at the same time and earlier, as an index of general poverty, but postneonatal mortality in North Wales has not been exceptionally high. In 1921-30 the highest risk of lung cancer was in and around London. In the modern data this was still true for older women, but for men and women under 45 years of age, and to a lesser extent for older men, the pattern has changed greatly; the epidemic has moved north, and highest risk is now in Northumberland and Durham. This spread appears to have occurred earlier for men than for women, and for urban than for rural areas, occurring latest of all for women in rural areas. Regional disparity has also increased, especially in males: risks in the northern regions are now over twice those in much of Wales and the South.