Major advances in our knowledge about the genetic determinants of osteoporosis have been made in recent years. They include the discovery of genes responsible for monogenic bone diseases associated with abnormal bone mass; the identification of quantitative trait loci for bone mass in the general population and in mice; and the characterisation of several candidate genes for osteoporosis. Information from these studies is being used to design new drugs for osteoporosis and to develop genetic markers for fracture risk assessment.