STUDY DESIGN - This primarily will be a descriptive, exploratory study describing the prevalence of osteoporosis in each of the 6 groups defined above. The diagnosis of osteoporosis will be based on bone densitometry studies. There are accepted densitometric criteria for the assessment of normal and abnormal bone mass. The criteria were largely developed in postmenopausal Caucasian women but reference values are also available for Caucasian, Black and Hispanic men. Normal bone density is described as a T-score less than -1. T-scores between -1 and -2.5 are indicative of osteopenia, and T-scores of less than -2.5 are indicative of osteoporosis. The prevalence of osteoporosis (T value less than 2.5) in each of the groups will be reported. Information on biochemical markers of bone turnover, vertebral fractures, and other risk factors will also be described.