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Studies of migrating populations have provided clues to potential causes of some types of cancers, but the data are often difficult to interpret because of the complex interaction of environmental, lifestyle and genetic (phenotypic) factors. A study from the UK London School of Hygiene and Tropical Medicine and University College and Middlesex School of Medicine (AJ Swerdlow) in the November, 1995 issue of the British Journal of Cancer (p 1312), attempted to unravel some of this complexity using selected immigrant populations. After independence, both Indian-born British and native Indian immigrants entered the UK. Both would have early life exposure to environmental features peculiar to India, but there would be phenotypic differences. These scientists looked at the two immigrant populations, with reference to UK vital statistics. Indian ethnics, and to a lesser extent British immigrants, showed elevated mouth & pharynx, gall bladder, and liver cancer in males and females, in cancers of the larynx and thyroid in men, and of the esophagus in women. Indian migrants had lower colon and rectal cancers and cutaneous melanoma for both sexes, for cancers of the ovary in women and of the bladder in men; this was not seen in British ethnics. Early life exposures also were clearly critical for increases in leukemia, and reductions in gastric and testicular cancers.