This review examines the hypothesis that there are gender differences in the relationship between bone mineral density (BMD) and fracture risk. Prospective studies of spine and hip fracture risk drawn from population samples suggest that the fracture risk increases as BMD decreases in men in the same way as that described in women. Moreover, for any given BMD at the spine, heel, or proximal femur the risk in men is similar to that in women. Although data are limited, prior fragility fractures increase subsequent fracture risks in both men and women. These studies suggest that the same BMD criteria used to diagnose osteoporosis in women can be applied to men.