Objectives: To validate usefulness of the three phase bone scan for the diagnosis of osteomyelitis in the diabetic foot with soft tissue inflammation. Materials and Methods: Fourteen diabetic feet with soft tissue inflammation were included in this study. We took the bone biopsy from the site of hot uptake on the three phase bone scan but no abnormal findings on the plain radiographs. We observed whether the bone has evidence of osteomyelitis on the patholgic findings such as inflammatory cell infiltration within bone, dead bone, new bone formation and fibrosis. Results: Thirteen of fourteen cases (92.8%) were compatible with osteomyelitis on the pathologic criteria. Inflammatory cell infiltration within bone was observed in thirteen cases, dead bone in twelve cases. new bone formation in four cases. fibrosis in eight cases. All of the four findings were observed in three cases. Conclusion: In the diabetic foot with soft tissue inflammation, the osteomyelitis should be included in differential diagnosis if the lesion reveals increased uptake on three phase bone scan, even though the lesion does not show any abnormal findings on the plain radiographs.