This four-year continuation proposes to add three data points, 9-10 months apart (T4-T6) to the four already collected (T0-T3), in order to complete eight years of follow-up including seven data points (bone density of two forearm sites) and six data points (spine bone density) on subjects in a cohort of 427 pre- and perimenopausal women born 1926-1936, of known representation of an original, community sampled cohort. The primary research questions for the proposed continuation are: 1) What are the normal rates of bone loss in an eight-year period, from pre- to postmenopause in the three sites and what are the independent effects of bone type (cortical vs. trabecular) and weight bearing? 2) How are transmenopausal endogenous hormone changes related to transmenopausal bone loss? and 3) Are there potential risk factors which affect the rate of bone loss and predict one or more subgroups of 'rapid' bone losers? To address these questions, prospective data are being collected for: the 3 bone sites; the following sex steroid hormones: Estrone, Estradiol, FSH, LH, SHBG, and DHEA-S: BMI, current drug use, exercise, diet, smoking and alcohol use. With the proposed data points, this prospective study will have sufficient follow-up to reliably estimate the normal rate of bone loss at menopause, as well as the factors likely to affect it. Major strengths of the study include; adequacy of numbers of subjects and follow-up; reliable measurement of bone density at 3 sites allowing independent comparisons of the effect of bone structure and weight bearing on bone loss; measurement of a wide range of potential risk factors for bone loss; known representation of the cohort; and application of the latest statistical techniques to complex longitudinal data.