The purpose of ICRP Publication 70 is to update information and reference values for the human skeleton. In keeping with the charge issued by Committee II in 1984 to update the original Reference Man (ICRP Publication 23), increased emphasis has been given to the normal biological variability among humans and to information on children. Also, an effort has been made here to provide a more extensive review of the literature on the skeleton, including the older literature, than was provided in the original document in 1975. An extensive review of the literature is to be distinguished from an exhaustive review, which is no longer a feasible task due mainly to the considerable amount of work that has been done in recent years in the general area of bone physiology. Nevertheless, every effort has been made to provide a representative cross-section of the available information on the skeletal features considered in this publication.