The inhibiting and destructive effects of roentgen rays on eiphyseal cartilage have been demonstrated in the animal by a number of investigators. During the first decade of the twentieth century Perthes, Recamier and Tribondeau subjected animals to irradiation, demomstrating that exposure to X-ray caused more or less retardation in the growth of bones and other structures. In later years, animal studies have been conducted by Barr, Bisgurd and Hunt, Regan and Wilkins. Their observations demonstrate without question that bone growth in the young can be retarded or stopped by a sufficient desage of X-ray. The literature does not divulage a large umber of cases in which longitudinal growth was followed after therapeutic irradiation about the epiphyses, although Desjardins, Stevens, Judy, Spangler and Frantz reported. We have observed a case of stunting of bone growth of 3 months age of infant followed after therapeutic X-irradiation of haemoangioma of right lower leg., The degree of retardation of bone growth were 8.0cm for the tibia and 2.6 cm for the fibula in four years after irradiation.