Blacks have a greater bone mass and a lower incidence of osteoporosis and hip fractures than whites. We performed biopsies of the iliac crest in 12 blacks (6 men and 6 women) and 13 whites (8 men and 5 women) who were matched for age (range, 19 to 46 years) and weight, to determine whether histomorphometric differences between blacks and whites could be identified. The static measurements of cortical and cancellous bone architecture were not significantly different in the two groups. In contrast, the dynamic measurements, determined with tetracycline markers, showed that the mean rate of bone formation in the blacks was only 35 percent of that in the whites (P less than 0.001). We conclude that the rate of bone turnover is lower in blacks than in whites, since bone resorption and bone formation are closely coupled in the steady state. If reconstitution of previously resorbed cavities at remodeling sites is incomplete in osteoporosis, a reduction in the rate of skeletal remodeling could provide a means for maintaining and preserving bone mass in blacks.