The procollagen peptides, ALP and osteocalcin evaluate a different osteoblastic function. With increased understanding of the precise functions of these markers and the factors that govern their biosynthesis and metabolic clearances, abnormalities in specific osteoblast activities may be discerned. It is hoped that further advances in research and development will provide assays with increased specificity, sensitivity, and availability. Clearly, measurement of bone markers does not substitute for bone mass measurement, the latter giving, at this time, the most useful information about fracture risk. The combined use of BMD and marker measurements, however, has the potential to be valuable in individual risk assessment. It is not clear whether a combination of markers or a single marker will gain the highest predictive results in this context.