The increasing number of immigrants in Sweden during the past four decades has brought the health of ethnic groups into focus. The purpose of this study was to analyse the influence of ethnicity, age, sex, marital status and date of immigration on suicide rates. The study population consisted of all individuals over 15 years of age, N = 6,725,274, from the Swedish census of 1985 and is based on individual data. Suicides and undetermined deaths, during the follow-up period 1986-1989, were taken from the central Cause of Death Register. Ethnicity, defined as being foreign-born, was a risk factor for suicide for both men and women with risk ratios of 1.21 (1.11-1.31) and 1.36 (1.21-1.53), respectively, with control for age and marital status. Being unmarried was also a risk factor for both males and females with risk ratios from 1.26 to 5.55 in different age groups. The highest risk ratios for suicide in Sweden, adjusted for age, were found among males born in Russia and Finland. They also showed higher suicide risks than in their countries of birth. Females born in Hungary, Russia, Finland and Poland all had high risks of committing suicide in Sweden and they also had higher risks than in their countries of birth. Further, being of male sex, aged 45-54 or 75 and older, and born in Eastern Europe or Finland were significant risk factors for suicide. The same was true for those who had immigrated to Sweden in 1967 or earlier and were born in Finland, Eastern Europe or in non-European countries. These findings are of great importance for primary health care and psychiatric care planning.