Total 40 cases of serial bone scans with Tc99-m -MDP performed on less than 24 hour, 2nd day, 3rd day, 5th day, 1 week, 4 week, 12 week and 1 year respectively after fractures in tibia were analysed. All 5 cases of bone scans performed within 24 hour after injury showed increase in generalized tracer uptake and 3 cases of them(60%) showed localized increase in tracer uptake at the fracture sites. The earliest bone sean performed 9 hour after injury showed generally and locally increased uptake at the fracture sites. All 5 cases of bone scan performed 1 year after injury sinowed localized increased uptake at the fracture sites and 2 cases of them (40%) showed generalized increase in tracer uptake. Bone scans performed 12 week after injury showed the most outstanding increase in generalized and localized tracer uptake. Bone scans performed 1 year after injury showed decreased amount of generalized increase in tracer uptake (but more increased uptake than normal) but the localized increase in traccer uptake at the fracture sites was observed persistently. More study should be needed to clarify the corelationship between the presence of cold spots during the fracture healing and the union of the fractures. It is difficult to differentiate the old fractures to fresh fractures with the bone scans performed within 1 year because of persistent increase in tracer uptake to 1 year after fracture.