BACKGROUND: Evidence from in vitro study indicates that bone marrow stromal cells and undifferentiated mesenchymal cells can different into chondrocytes.OBJECTIVE: To observe the morphological changes of red bone marrow and periosteum allograft and its capability of chondrogenesis after transplantation in rabbits for repair of articular cartilage defects.DESIGN: Randomized controlled experiment with rabbits.SETTING: Department of Human AnatomY, Medical College of Yanbian University.MATERIALS: Fourteen Chinese rabbits of either sex with body mass of (2.15±0.30) kg.METHODS: This experiment was carried out in the Department of Human Anatomy, Medical College of Yanbian University between April 2001 and February 2002. Full thickness articular cartilage defect of 3.0 mm×6.0 mm was produced in the rabbits on the patellar surface of the femur in the 28knee joints, which were then randomized to receive either transplantation with autologous red bone marrow and periosteum graft into the bone defect (20 knees) or no grafts (8 knees). The morphological changes of graft were evaluated 7 days and 2, 4, 8, and 12 weeks after the operation by gross,optical microscopic, and electron microscopic observations with also assistance of image analysis.drocyte area of two groups.RESULTS: In the 12th week after the operation, the morphology, distribution and arrangement of the regenerated tissues were similar to normal cartilage in the knees with graft transplantation, and the regenerated tissues grew to be integrated with the surrounding normal cartilage with obscure boundary between them. But the boundary between the bone defect and surrounding normal cartilage was clearly observed in the ungrafted knees,and most of the defect was replaced by fibroblasts and collagen fibers with only some small chondrocytes seen in the superficial layer. Microscopic observation in the 4th week revealed the presence of chondrocytes in the superficial layer of the graft, and imaging analysis displayed greater single cell surface in the grafted than in the ungrafted knees in the 4th, 8th and 12th weeks [(248.70±16.62) vs (168.23 ±6.14) μm2, (267.79±28.88) vs (172.93±17.18) μm2, (175.75±13.24) vs (145.35±13.54) μm2, P ＜ 0.05].CONCLUSION: The chondrogenesis in autologous complex tissue graft of red bone marrow and periosteum occurs 8 weeks after the operation, and the morphology, distribution and arrangement of the newly generated cells are similar to that of the normal cartilage, with good mutual compatibility and complementarity in the regeneration activity between the two graft tissues.