Abstract
1. Grafts of joint cartilage from immature lambs were used to repair articular cartilage defects in other lambs and in adult sheep.
2. Stability of these grafts in a functional state was found in most for periods up to fourteen months. Although a limited homograft reaction occurred this did not lead to destruction of the cartilage, even though parts of it were well vascularised.
3. The results suggest that the process of endochondral ossification is associated with the liberation of antigenic material leading to sensitisation of the host. Destruction ofthe cartilage is prevented by an inhibitory action which the matrix appears to exert on the destructive elements themselves and which is itself dependent on the vitality of the chondrocytes.
4. The avascularity of cartilage is not a sufficient explanation for its privileged position in relation to the homograft reaction.
