Twelve rabbits were used in this investigation. They were divided into 3 groups: A, B and C (4 rubbits each). The medial meniscus was..r..*d from the right knee joint of groups B and C. Animals of group A were sham-operated and used as control. The animals were sacrificed I month (group B) and 2 months (group C) after meniscectomy. The articular cartilage of the medial and lateral femotal condyles of the right knee joint was carefully removed and processed for both light and electron microscopic examination. Variable degrees of degenerative changes were observed in the articular cartilage of the medial femoral condyle. No signs of degenerative changes were observed in the articular cartilage of the lateral femoral condyle. One month after the operation, cells of the superficial layer were completely lost and proliferation of chondrocytes in the deeper layer were observed. By 2 months, the superficial layer was completely lost with marked hypocellularity of the deeper layer. These degenerative changes were confined to an area of the articular cartilage while the rest appeared almost similar to that of the control. It is suggested that this affected area is more vulnerable to meniscectomy. It is concluded in this investigation that the meniscus is an important structure protecting the articular cartilage from undergoing degenerative changes. The results may also shed some light on the possible postoperative undesirable changes in football players who usually undergo meniscectomy after atear in the medial meniscus.