Mortality, criminality and mental illness among young adults were studied in an unselected birth cohort of 12 058 children born live in Northern Finland during 1966. The cohort members were followed up to the age of 27 years. The total number of all deaths was 117, and 79.5% of these deaths were from unnatural causes. The mortality of males was more than threefold higher than that of females. There was a significantly higher mortality risk in men with schizophrenia (OR, 9.31; 95% CI, 3.14-25.53), other psychoses (OR, 10.28; 95% CI, 2.40-37.02), personality disorders (OR, 4.28; 95% CI, 1.04-14.67) and combined personality disorders and criminality (OR, 3.27, 95% CI, 0.99-9.59). In the group of major mental disorders, 75% of deaths were suicides.