Objective To evaluate osteogenetic effectiveness of hyaluronic acid (HA) mixed with adenovirus mediated human bone morphogenetic protein-2 gene(Adv-hBMP-2) transfected bone marrow derived mesenchymal stem cells (BMSCs) in the repair of radial shaft defects of rabbits. Methods The BMSCs were collected from bone marrow of rabbits, cultured and transfected by Adv-hBMP-2 in vitro. The radial shaft defects (1.5 cm) models in 20 rabbits (40 sides) were created and then injected the cells and/or materials respectively in the following four groups(n=10): Group 1: Adv- hBMP-2 transfected BMSCs+HA; Group 2: Adv-hBMP-2 transfected BMSCs; Gourp 3: HA; Group 4: control.Roentgenography, histological exam￡?biomechanical test and histomorphometrical analysis were studied at various time points. Results The bone defects of 6 out of 8 sides in Adv-hBMP-2+HA Group in the 12th week after injection were repaired completely. At the same time, only 3 sides were repaired completely in Adv-hBMP-2 Group, and none was repaired completely in HA Group and control Group. The X-ray scoring system revealed that the average scores in each groups were 4.63±0.74, 3.38±1.60, 1.63±0.74 and 1.50±0.53, respectively. In the groups of Adv-hBMP-2+HA and Adv- hBMP-2, histological examination revealed that there were much woven callus formation in the sites of the bone defects in the 4-8th week after injection and partial bone marrow cavities were revasculized and lots of osteons were formed in the 12th week after injection; while in HA group and control group, the sites of bone defects were mainly full of fibrous tissue and no complete healing happened. Two ends of the bone defects were hardened. The histomorphometrical analysis showed that the new trabecular bone area in Adv-hBMP-2+HA group and Adv-hBMP-2 group were 16.25±3. 49mm2 and 10.39±2.02mm2, respectively, which has statistically significant difference (P<0.001). The biomechanical test showed that the maximum vertical loading and elastic modulus were (211.54±63.58) N and (113.36±56.47)MPa in Adv- hBMP-2+HA group, and (126.74±53.13 )N and (98.91±63.36)MPa in Adv-hBMP-2 group (P<0.05).The ratios of average maximum vertical loading/normal value of radial shaft in the groups of Adv-hBMP-2+HA and Adv-hBMP-2 were 75.86% and 45.45%, respectively. Conclusion The tissue-engineered bone made by HA mixed with Adv-hBMP-2 transfected BMSCs can repair the bone defects in the radial shaft of rabbits.