Increasingly, social scientists are turning to childhood to gain a better understanding of the fundamental social causes of adult mortality. However, evidence of the link between childhood and the mortality of adults is fragmentary, and the intervening mechanisms remain unclear. Drawing on the National Longitudinal Survey of Older Men, our analysis shows that men's mortality is associated with an array of childhood conditions, including socioeconomic status, family living arrangements, mother's work status, rural residence, and parents' nativity. With the exception of parental nativity, socioeconomic-achievement processes in adulthood and lifestyle factors mediated these associations. Education, family income, household wealth, and occupation mediated the influence of socioeconomic status in childhood. Adult lifestyle factors, particularly body mass, mediated the effects of family living arrangements in childhood, mother's work status, and rural residence. Our findings bring into sharp focus the idea that economic and educational policies that are targeted at children's well-being are implicitly health policies with effects that reach far into the adult life course.