Cancer incidence in migrants to New South Wales (NSW) from individual countries within the British Isles has been compared with that in the Australian-born population using data from the NSW Central Cancer Registry for the period 1972-84. Indirectly age-standardised incidence ratios (SIR) showed that, for cancer at all sites combined, Scottish migrants had a significantly higher, and English migrants a lower, incidence than the native-born Australians. Melanoma of skin was less common in migrants from all four countries while lung cancer was more common. In all except the Irish migrants, stomach cancer was more frequent than in the Australian-born. Raised SIRs for bladder cancer were found in men from all the countries and for breast cancer in all except the Irish women but only in the English migrants were these ratios significant. English migrants differed from those from Wales, Scotland and Ireland in that, compared with the Australian-born, they had significantly lower SIRs for cancer of the colon (both sexes), head and neck, larynx and prostate (men), gallbladder and kidney (women), and a higher SIR for ovarian cancer. Bone cancer was relatively more common in men born in Wales. 'Other genital' cancers (penis and scrotum; vulva and vagina) tended to be more frequent in migrants from each country than in the Australian-born.