This study employs a life course perspective in its examination of possible antecedents of premarital as well as marital conceptionsearly in the lives of young women and men in Great Britain. Using data on 5,167 women and 5,585 men from the British National Child Development Study, it is found that significant antecedents of premarital conception for both sexes are low socioeconomic status, low adolescent social adjustment, and a family environment characterized by parent-child arguing, parental divorce or separation, or a family history of nonmarital fertility. Pubertal development is found to be related only weakly to premarital conceptions. These findings are compared to analyses of marital conception for the same cohort.