Unlike hyaline cartilage, mandibular condylar cartilage can respond to injury by complete healing. We have used the reparative potential of mandibular cartilage to promote repair of defects in a hyaline cartilage joint surface. In 12 adult marmosets, articular fibrocartilage from the mandibular condyles was transplanted into full-thickness defects created in the femoral condyles. Additional defects acted as an ungrafted control group. The grafted defects showed good incorporation of the transplant with restoration of the articular surface within six months. Repair was by proliferation of the fibrocartilaginous graft and chondrogenesis of hyaline cartilage. The repopulating cells were distributed in a matrix of maturing collagen and sulphated glycosaminoglycans. Ungrafted control defects were only partly repaired with fibrous tissue, leaving articular deficiencies. We conclude that transplanted mandibular fibrocartilage can promote reconstitution of wounded hyaline cartilage joint surfaces in primates