OBJECTIVE To examine the relation between childhood adversity, the role of school performance, and childhood psychopathology and the risk of suicide. DESIGN Cohort study of register based indicators of childhood adversity (at ages 0-14) including death in the family (suicide analysed separately), parental substance abuse, parental psychiatric disorder, substantial parental criminality, parental separation/single parent household, receipt of public assistance, and residential instability. SETTING Swedish medical birth register and various Swedish population based registers. PARTICIPANTS 548 721 individuals born 1987-91. MAIN OUTCOME MEASURES Estimates of suicide risk at ages 15-24 calculated as incidence rate ratios adjusted for time at risk and confounders. Results Adjusted incidence rate ratios for the relation between childhood adversity and suicide during adolescence and young adulthood ranged from 1.6 (95% confidence interval 1.1 to 2.4) for residential instability to 2.9 (1.4 to 5.9) for suicide in the family. There was a dose-response relation between accumulating childhood adversity and risk: 1.1 (0.9 to 1.4) for those exposed to one adversity and 1.9 (1.4 to 2.5) and 2.6 (1.9 to 3.4) for those exposed to two and three or more adversities, respectively. The association with increased risk of suicide remained even after adjustment for school performance and childhood psychopathology. CONCLUSION Childhood adversity is a risk factor for suicide in adolescence and young adulthood, particularly accumulated adversity. These results emphasise the importance of understanding the social mechanisms of suicide and the need for effective interventions early in life, aiming to alleviate the risk in disadvantaged children.