Sweden will soon have a million foreign-born residents, representing almost 11 per cent of the population. As shown in the article, migration to Sweden is a continuing process rather than an isolated life event; for example, half of those who emigrated to Sweden in 1968 had returned to their home country or proceeded to a new country by 1988. The possible effects of the migration process upon immigrants, and the ensuing impact on primary health care, are examined in the article. Published findings suggest that immigrants--whether they migrate because of war, political or religious persecution, or for economic reasons--may experience increased stress, thus exacerbating any individual susceptibility to illness. Strategies for future research in migration medicine and primary health care are also discussed.