BACKGROUND: Childhood and adolescent mortality accounts for a substantial proportion of years lost prematurely. Reducing childhood and adolescent mortality relies on knowing characteristics of those at elevated risk of dying young. We therefore aimed to identify such characteristics; our main hypothesis is that psychosocial adversity in infancy is linked to increased mortality rates in childhood and adolescence. METHODS: We conducted a register-based cohort study involving all 1,549,581 children born to Danish-born parents in Denmark between 1 January 1981 and 31 December 2010. For each infant, we extracted data relevant to Rutter's indicators of adversity (low social class, parents not cohabiting, large family size, paternal criminality, maternal mental disorder, and placement in out-of-home care). Follow-up began on the cohort member's first birthday. We estimated the association between adversity score (the number of Rutter's indicators of adversity present in infancy) and death via. Cox regression. RESULTS: During follow-up (18,874,589 person-years), 2,081 boys and 1,420 girls died before or on their 18th birthday. The hazard ratios for death were 2.3 (95% CI = 1.9, 2.9) and 2.1 (95% CI = 1.6, 2.7) for boys and girls with adversity scores of 3-6 compared with those with a score of 0. These associations were driven by causes of death with known links to psychosocial adversity. CONCLUSION: While absolute mortality rates were low, infants with adversity scores of 3-6 were approximately twice as likely to die prematurely compared with infants with adversity scores of 0. Whether these associations generalize to other countries should be subjected to further study.