It is the purpose of this communication to report a method of prediction, for use in epiphyseal arrests, which is based upon cumulative roentgenographic measurements of the femur and of the tibia in growing children. It is proposed, also, to outline the experiences with epiphyseal arrests at The Children's Hospital, Boston, regarding both the accuracy of the predicted effect and the incidence of deformities . . . The chart which is presented for use in prediction must be considered a tentative one, and it will be revised as more data are accumulated. It represents a part of the material from a study of growth which has been in progress since 1940. This study involves approximately 700 children, 87 per cent of whom have residual paralysis in one lower extremity with a normal extremity on the other side; and it also includes observations on 158 normal children . . .