Although various environmental factors, including diet and physical exercise, influence bone mass, a genetic contribution to this parameter has also been recognized. Genetic linkage analyses and candidate gene association studies have implicated several loci, and a variety of candidate genes in the regulation of bone mineral density and the pathogenesis of osteoporosis or osteoporotic fracture. However, the genes responsible for these latter conditions have not been identified definitively. I here summarize both the candidate loci identified by linkage analyses and the candidate genes examined by association studies. I also review in more detail studies that have examined the association with bone mass or with the susceptibility to osteoporosis or osteoporotic fracture of polymorphisms in the genes for the vitamin D receptor, collagen type Iα1, estrogen receptor α, interleukin-6, osteocalcin, osteoprotegerin, CC chemokine receptor 2, matrix metalloproteinase-1, and transforming growth factor-α1. Such studies may provide insight into the function of these genes as well as into the role of genetic factors in the development of osteoporosis.