Vascularized fibular graft is one of the treatment option for avascular necrosis of femoral head (ANFH) and has been known as providing a strut mechanical support and new vascular bed. It is very important to evaluate a healing process in femoral head after vascularization procedure. But a plain radiographic finding has a problem to assess pathological changes of ANFH treated with vascularized fibular graft. Authors analyzed chronogical changes of Tc-99m-HDP bone scan in 31 cases of ANFH treated with vascularized fibular graft from April, 1991 to May, 1994 and following results were obtained. l. Until 2 months after surgery, no change in size of cold defect area and no significant change in extent of RI uptake in reactive zone were noted. 2. During 2 months and 6 months after surgery, slight decrease in size of cold defect area and minimal changes in extent of RI uptake in reactive zone were observed. 3. During 6 months and 12 months after surgery, size of cold defect area decreased to 1/2 and changes in extent and degree of RI uptake in reactive zone were observed. 4. During 1 year and 2 years after surgery, size of cold defect area were minimal and sometimes faded away. RI uptake with decreased density in reactive zone broadened and moved to subchondral area. 5. After 2 years after surgery, cold area faded away and small increased RI uptake were observed in same site. In conclusion, Tc-99m-HDP bone scan which is economic and easily applicable in a patient is very useful for follow up study in ANFH treated with vascularized fibular graft.