Objectives. To investigate the effect of basic fibroblast growth factor (FGF-2) on root resorption following delayed autotransplantation in dog.Study design. Mandibular second and third premolars of beagle dogs were extracted to create sites for autotransplantation. After two months, in the experimental sites, the first and fourth mandibular premolars were extracted and air-dried prior to autotransplantation with the application of recombinant FGF-2, while control sites received teeth without FGF-2. At 2, 4, or 8 weeks after surgery, the animals were sacrificed and specimens collected and processed for histological examination.Results. Autotransplantation with FGF-2 yielded formation of new periodontal ligament-like tissues with inserting collagen fibers, associated cementum and bone. The occurrence of replacement resorption in the FGF-2 treated group was significantly lower than that in the control group (P < .01). Conclusion.It was demonstrated that topical application of FGF-2 reduced the occurrence of ankylosis and root resorption following delayed autotransplantation in this experimental model.