Abstract Immigrants in Sweden have the same rights as natives to benefit from the national social insurance system and legally they have equal access to medical care. There are, however, a number of reasons why immigrants may exhibit different illness behaviour compared to the native population. In a record linkage study the hospital utilization during 15 months (January 1976–March 1977) by Swedes and immigrants and by Swedes and two groups of immigrants, Finns and Mediterraneans, was compared. The study population (17,004 people) was a 10% sample of the population in a Stockholm district. Compared to Swedes, immigrants more often used hospital emergency departments but less often hospital outpatient clinics. Immigrants receive more fragmented and episodic care which may lead to more emergency visits. The illness behaviour was more similar for Swedes and Finns than for Swedes and Mediterraneans. The highest utilization rates had Mediterranean women. Twenty percent of their hospital admissions were diagnosed as symptoms and illdefined causes. Institutional barriers that guard outpatient clinics and to a certain extent health centers and private physicians and make these institutions less accessible to immigrants than natives may explain some of the differences found in the study.