This dissertation features two manuscripts that appeared recently in peer-reviewed publications, and a third report, submitted for publication, that identify biochemical and genetic factors that help explain the wide variability of bone mineral density (BMD) measured by dual X-ray absorptiometry in a population of 226 healthy, elderly female volunteers. After the Introduction section, each manuscript is prefaced by a foreword and appears in a separate chapter. The first publication compares the diagnostic efficacy of two biochemical markers of bone metabolism for identifying women with decreased BMD. This report highlights the wide differences between individuals in the circulating levels of specific biochemical markers of bone resorption and formation in healthy women. Based on these findings, our immediate goal was to identify factors that help explain such broad variability in BMD and circulating levels of biochemical markers of bone turnover in elderly subjects. Our preliminary evidence indicated that measurement of biochemical markers of bone metabolism in serum enables the identification of subjects with osteoporosis.