Tissue engineering has become a new approach for repairing bone defects. Previous studies have been limited to the use of slow-degradable scaffolds with bone marrow stromal cells (BMSCs) in mandibular reconstruction. In this study, a 30 mm long mandibular segmental defect was repaired by engineered bone graft using osteogenically induced autologous BMSCs seeded on porous beta-tricalcium phosphate (beta-TCP, n=5). The repair of defects was compared with those treated with beta-TCP alone (n=6) or with autologous mandibular segment (n=4). In the BMSCs/beta-TCP group, new bone formation was observed from 4 weeks post-operation, and bony-union was achieved after 32 weeks, which was detected by radiographic and histological examination. In contrast, minimal bone formation with almost fibrous connection was observed in the group treated with beta-TCP alone. More importantly, the engineered bone with BMSCs/beta-TCP achieved a satisfactory biomechanical property in terms of bending load strength, bending displacement, bending stress and Young's modulus at 32 weeks post-operation, which was very close to those of contralateral edentulous mandible and autograft bone (p>0.05). Based on these results, we conclude that engineered bone from osteogenically induced BMSCs and biodegradable beta-TCP can well repair the critical-sized segmental mandibular defects in canines.