Ordinary measurements of the wall thickness (the end result of the osteoblastic work) of trabecular bone packets (completed remodeling sites) describe the average thickness of walls formed during the previous two to three years. If the bone biopsy is obtained shortly after onset of disease or initiation of treatment, only a few of the measured sites will represent walls formed under the new conditions. With a reconstruction of the formative site true information of the performed osteoblastic work can be obtained, since it is based upon observations of the actual formative events and not the end result (completed walls). Previously published methods have the disadvantage of being time consuming and technically difficult. Furthermore, the method by Eriksen et al. includes rather complicated mathematical calculations. In the present study a new method for reconstruction of the formative phase is presented, which can be performed from measurements normally obtained in a routine histomorphometric analysis and from paired values of osteoid thicknesses and uncompleted wall thickness. The method does not introduce a new time consuming step in the histomorphometric analyses of the bone biopsy. Furthermore, calculations needed to reconstruct the events of the formative phase can easily be performed using a personal computer and a spreadsheet. The new method for reconstruction presented in this paper gives growth curves for matrix and bone mineral, which are virtually identical with the growth curves previously published by Eriksen et al. for the same 20 normal individuals.