In this article we describe the use of dual-energy X-ray absorptiometry (DXA) technique in the study of fetal and infant bone development. In particular, we review the results of densitometric studies on human developing dry bones such as spine, femur, and mandible; these data are compared with the results obtained with other methods used in the past. In particular DXA technique applied in dry is able to detect the first appearances of the ossification centers; show individual variability of bone mineral density yet during the prenatal life; and determine the correlation between bone mineral density and the variation of mechanical loading.