This study was performed to validate the clinical usefulness of meniscal replacement using a autogenous rib cartilage after meniscectomy in rabbits. The materials used for the study consisted of 20 rabbits, weighing between 1.8 and 2.5 Kg. The morphological and histological characteristics of the transplanted autografts and medial femoral condylar articular cartilage were observed at 2, 4, 9, 12 weeks postoperatively. Five rabbits were sacrificed in each time intervals. The results were as follows; 1. The lateral part of the replaced rib cartilage was tightly attached to the synovium at 4 weeks. The synovium covered the whole part of grafted cartilage at 9 weeks. The contact surface of the grafted cartilage to the femoral condyle was flattened at 12 weeks. 2. The replaced rib cartilage was survived in the joint. Histologically the synovium was regenerated around the grafted cartilage at 2 weeks and 4 weeks. The hyaline cartilage cells of the rib cartilage were replaced to the fibrous cartilage cells at 9 weeks. The rib cartilage was totally replaced with fibrous cartilage at 12 weeks. 3. The destructive change of the articular cartilage cells of the femur was started at 2 weeks. The destructive change was progressed. The erosion, fibrillation and debris of the articular cartilage and regeneration of the cartilage cells were observed at 12 weeks. There were no destructive change in the subchondral bone area. Even though there were the destructive change on the femoral articular cartilage. It will be regenerated because of the subchondral bone was intact, Therefore, it will be considered that a autogenous rib cartilage might be used the meniscal replacement materials.