Background: A large number of biosocial variables have been shown to associate with age at menarche, but the results are inconsistent and differentiate not only between countries but within countries as well. Aim: This study examined age at menarche in a British national cohort in relation to 21 biosocial and anthropometric variables. Subjects and methods: The analyses were based on 4483 girls from the British National Child Development Study (NCDS). Results: The majority of girls reached menarche between 12-14 years of age. Girls from smaller families, those living in the East and South East, South West, West Midlands and Wales regions, in tied housing and uncrowded conditions, not sharing a bedroom, not having free school meals, whose families lived in households without financial problems had started menstruating earlier than their peers from families with lower socioeconomic status. However, when all the significant variables were analysed together significant associations remained only for mother's age at menarche, height and weight at 7 years, family size and tenure. Conclusions: The results of this study support the hypotheses that intra-uterine growth and conditions in early life as well as socio-economic background are associated with the timing of menarche and that greater childhood growth and better SES are related to earlier menarche.