Osteoporosis is a major public health problem that affects the entire aging population. This report provides an update on the epidemiology of osteoporosis and its associated fractures. Published studies from 1997 to the present are highlighted. The current US prevalence estimates for osteoporosis, trends in fracture incidence rates, and latest reports on the morbidity, mortality, and costs attributable to osteoporotic fractures are discussed. Recent advances in our understanding of risk factors associated with osteoporosis and related fractures are reviewed. Special attention is paid to the rapid progress being made in the field of genetics, the growing importance of nutrition, and the new questions being raised as to the influence of hormonal factors on bone mineral density and fracture risk. New studies linking osteoporosis to several other important diseases in women including breast cancer, osteoarthritis, and stroke are also reviewed.