This project aims to identify major environmental influences on hip structure in childhood, by testing hypotheses for how expansion of the inner and outer surfaces of the hip bone is controlled during growth. This will be achieved by exploiting the unique Avon and Longitudinal Study of Parents and Children (ALSPAC) birth cohort, in which children born in Avon between 1991-2 have been followed up in detail since before birth. We will investigate the relationship between environmental factors recorded in ALSPAC, and hip structure as assessed at age 13 using a low energy x-ray technique. By improving our understanding of the deterimants of hip structure in this way, the present proposal is intended to shed light on the childhood origins of hip fracture in later life, and provide a basis for population-based strategies aimed at reducing the prevalence of this common condition.