The aim of this study was to examine whether the hypothesized association between country of birth and suicide rates remains after adjustment for age, marital status, socioeconomic status, and hospitalization due to psychiatric disorders or substance abuse. A Swedish cohort of 4.4 million individuals aged 25-64 years was followed from January 1, 1994, to December 31, 1999 for suicide. Suicide rates varied according to country of birth. Among men the highest risk of suicide was found among men from Finland. Among women the highest risk of suicide was found among women from Finland, Poland, and Eastern Europe. Key factors to prevent suicide include early detection and treatment of psychiatric disorders and/or substance abuse, especially among certain population groups.