PIP: This paper reports the results of a systematic review of mortality among immigrant groups in England and Wales. Mortality rates in 1970-72 were compared with rates both in the countries of origin and in England and Wales. All-cause male mortality was lower in immigrants from italy, the Caribbean, and Poland than in the countries of origin, suggesting a selection effect among migrants. The opposite patttern was noted for imigrants from Ireland, however, indicating social and health disadvantages may be a stimulus to migration. The high mortality from tuberculosis in immigrants from the indian subcontinent and Ireland, low mortality from ischemic heart disease and high mortality from cerebrovascular disease in Caribbean men, and low mortality from cancer of the lung and intestine in all but Irish men reflect the influence of the migrants' original country. A possible influence of the host country on determining disease rates is seen in adaptation of immigrant mortality ratios toward the England and Wales average. For example, immigrants from several countries analyzed had ischemic heart disease mortalty ratios intermediate between those for the original country and for England and Wales. In addition, British people born in the Indian subcontinent showed a mortality pattern intermediate between that of the Indians and the England and Wales average, supporting the argument that environmental rather than genetic determinants may be involved in the principal chronic diseases. Particularly high mortality from complications of pregnancy and childbirthwas noted in indian and Caribbean immigrants, indicating that there may be social and cultural barriers to the receipt of adequate medical care. Finally, social class differences did not account for mortality differences among immigrant groups. Mortality was higher for the Irish than the English or Welsh in each social class group, which suggests there are cultural influences on mortality that act independently of social class influences.