Large increases in serum alkaline phosphatase (ALP) concentrations after fractures in elderly patients have been noted in specialist journals, but standard textbooks either make scant reference or comment that there is little or no rise. Measurements of biochemical parameters appear to be the only objective evidence of the changes occurring during bone regeneration. The aim of this study was to examine whether the assessment of Serum bone specific ALP as a biochemical parameter in the early posttraumatic phase may indicate the course of fracture healing. The level of serum alkaline phosphatase is often valuable in the diagnosis of metabolic bone disease but rises after any uncomplicated fracture, and since such a rise may limit the diagnostic usefulness of this measurement. We studied alkaline phosphatase concentrations in young and elderly patients who had been admitted to an orthopaedic ward because of a fracture and to be continued in our endeavour to find a bone turnover marker as a diagnostic or prognostic tool for monitoring bone healing.