Ancient cemeteries are often characterized by a considerable number of infants and young children. Sex differences in childhood mortality, however, could rarely be studied up to now, mainly because there were only few proven traits for sexual determination of immature skeletons. Based on a historic sample of sixty-one children of known sex and age from Spitalfields, London (37 boys, 24 girls), sexually distinctive traits in the mandible and ilium are presented for morphognostic diagnosis. Besides other features, boys typically show a more prominent chin, an anteriorly wider dental arcade, and a narrower and deeper sciatic notch than girls. Most of the traits presented in this study allow individuals between birth and five years of age to be successfully allocated to either sex in 70–90% of the cases. © 1993 Wiley-Liss, Inc.