We study the importance of childhood socioeconomic conditions in predicting differences in life expectancy using data from a large sample of children collected in 16 locations in England and Scotland in 1937-39, who have been traced through official death records up to 2005. We estimate a number of duration of life models that control for unobserved family heterogeneity. Our results confirm that childhood conditions such as household income and the quality of the home environment are significant predictors of longevity. Importantly, however, the role of socioeconomic status appears to differ across cause of death, with household income being a significant predictor of death from smoking-related cancer. Moreover, we find that (1) poor housing conditions in childhood is associated with reduced longevity, that (2) early doctor-assessed childhood health conditions significantly predict a reduced length of life, that (3) children born in a location with relatively high infant mortality rates live significantly fewer years, and that (4) there is a high correlation in longevity across children from the same family across all causes of death. We estimate that the difference in life expectancy between those with the 'best' and 'worst' observable characteristics is about 9 years, which increases to 20 years when we take into account the 'best' and 'worst' observable and unobservable household characteristics.