Freeze-dried bone allograft (FDBA) has been used extensively in periodontal surgery and in the treatment of pocket osseous defects resulting from inflammatory periodontal disease. No other endodontic investigation has used this type of graft material in the treatment of bony resorptive defects of the periapical lesions associated with failed endodontic therapy. Therefore this study was conducted with the use of FDBA, to assess healing ability of osseous defects after removal of periapical lesions associated with failed endodontically treated teeth. In all patients periapical lesions were surgically removed with retrograde amalgam seal and the graft material was then carefully packed without pressure into the bony defect. The lesions were fixed in 10% neutral buffered formalin and prepared for histologic examination. Long-term recall demonstrated bone regeneration and good tolerance of allograft material by the periapical tissues. The periapical lesions were either periapical granulomas or apical periodontal cysts. We conclude that FDBA is a biocompatible material of osteogenic potential and can be used effectively in treating osseous defects of periapical lesions associated with failed endodontically treated teeth.