In 12 JCA patients with severe mandibular hypoplasia, who all strongly demanded early treatment, 21 mandibular condyles were replaced by costochondral grafts. All of them had radiographic morphological changes in the mandibular condyles with varying degrees of destruction of the articular cartilages. Severe pathological changes in the lower joint compartments were consistently observed at surgery. Hence, the lower joint compartments were obstructed with granulomatous tissue, whereas the upper compartments were without macroscopic pathological changes. These findings indicated a polarized involvement of the temporomandibular joint (TMJ) in juvenile chronic arthritis (JCA). The extent of condylar articular surface destruction at histological examination varied from focal to total cartilage destruction. Inflammation of the subchondral bone marrow was a frequent finding. In spite of considerable arthritic destruction of the condyles, only one patient had TMJ pain, while a restricted mouth opening capacity was a more frequent finding. Thus, TMJ pain did not seem to constitute a reliable symptom of serious arthritic destruction of the mandibular condyle.