The morphologic changes of articular cartilage with bone grafting to fill subchondral bone defects were studied in 23-month-old New Zealand rabbits with bilateral tibial subchondral bone defects. The defects were made approximately 5 mm below the articular surface and were covered with surrounding tissues. The right side was filled with calcium sulfate bone graft, and the left side was filled with acrylic cement as control. The articular cartilage above the fillers was harvested 12 weeks postoperatively. Gross observation, histological examination, and transmission electron microscope observation were undertaken. The results showed that cartilage above the calcium sulfate had a normal hyaline articular cartilage appearance. In contrast, cartilage above the acrylic cement showed degenerative changes in both histological and electron microscope observation. These results suggest that using calcium sulfate bone graft to fill subchondral metaphyseal bone defects has no harmful effect to overlying articular cartilage. This substitute can reduce the possibility of osteoarthritis compared to acrylic cement.