Using the existing bone measurement data base from the Young Women's Health Study, we have identified 24 study participants with low, average and high total body bone densities. We will use bone density measurements of their biologic mothers to: determine if a positive corelation exists between adult maternal total body bone density and 16 year old daughter total body bone density; determine if a correlation exists between adult maternal hip bone density and content and between 16 year-old daughter hip bone density and content; determine if a correlation exists between adult maternal bone density and/or content and rate of bone acquisition for the daughters from ages 12-16.