An attempt has been made to substantiate the feeling of others that osteochondritis dissecans, perhaps more appropriately termed osteochondrosis dissecans, is not a clinical entity in itself but is probably a type of osteochondrosis, the etiology of which is not understood. Various etiological theories have been proposed. The occurrence of osteochondritis dissecans in various members of a family, associated with osteochondrosis deformans tibiae of the adolescent type, while possibly coincidental, is most suggestive of some common etiological factor and further supports the theory of heredity. In the author's cases the presence of osteochondritis dissecans probably preceded, from a chronological viewpoint, the development of tibial bowing. From a genetic viewpoint, it is interesting that the mother of the patients showed neither osteochondritis dissecans nor bowing. The father and two sons illustrate the coexistence of osteochondritis dissecans and adolescent tibia vara, whereas the daughter demonstrated the presence of osteochondritis dissecans without adolescent tibia vara (Chart I). The paper is not intended to propose any new theories regarding etiology or to discuss treatment in detail. The ill timing of osteotomy is clearly demonstrated. If the deformity is sufficiently severe to warrant osteotomy, this procedure should be postponed until bone maturity is reached; otherwise recurrence of the deformity is likely. Controlled epiphyseal retardation by the use of staples in the lateral portion of the upper tibial epiphysis is recommended as a more conservative form of operative treatment.