It is proposed that the cartilage of the mandibular condyle is not the site of active growth but rather that of secondary adaptive and remodeling responses. Experiments were conducted in M. irus monkeys replacing the surgically excised mandibular condyle with either a sliding ramus graft or a costochondral rib graft. After 2 years the characteristics of the grafts were examined. Both techniques produced acceptable functional condyles; when examined histologically, the condyle formed from the rib graft was shown to be closely comparable to the condyle on the unoperated side. The functional condyle formed by the sliding ramus graft lacked the histologic features of the normal condyle and showed less capacity for remodeling and adaptation. It is proposed that the histologic nature of the grafts used to restore the condyle could have a profound influence on subsequent growth and development. The costochondral graft is readily available, possesses the necessary mechanical properties, and has the capacity for remodeling into an adaptive mandibular condyle. These properties make it eminently suitable for use in reconstruction of the condyle in both the growth period and adult life; when placed correctly in the fossa, and facial height and symmetry are restored, the resultant condylar head adapts and responds to the demands of the functional matrix, thus permitting mandibular growth.