The growing incidence of juvenile delinquency during the past years has become a serious concern of the general public and the authorities. Following the lead taken by the Home Office, a number of local authorities, child guidance clinics and welfare agencies have instituted inquiries into the causes and conditioning factors of juvenile crime from the social, economic and medico-psychological points of view. The institutions for the mentally defective have been faced with the same problem through the increasing number of cases referred by the juvenile courts, and Dr. D. Turner, in his Annual Report on the Royal Eastern Counties Institution, Colchester, for the year 1943, called attention to the difficulties of their management within an institution of the usual type. The question calls urgently for a settled policy regarding their disposal and treatment, and it goes without saying that this can only be attained on the ground of a better insight into the psychology of the delinquent defective.