For the unity of the medical profession. The debate about specialization in Belgium (1900-1940) This article focuses on the debate about specialization in the interwar period in Belgium. It illustrates the opposition between the scientific segment of the profession, represented by the Royal Academy of Medicine and the medical faculties on the one hand and the professional organizations of medical practitioners on the other hand. In many places, general practitioners practised part-time as specialists. The first group emphasized the importance of a reorganization of medical education and, in second order, better supervision of medical practice. Some members of the Academy were alarmed by the damage done by gp's in the field of surgery and ophthalmology. The professional organizations were concerned about the fact that specialization was closely linked to the development of institutions, such as outpatient's clinics and hospitals, which were sometimes linked to sickness funds, the socialist sickness fund in particular. Their main objective was to keep medical practice open to all practitioners and out of the hands of the sickness funds. Problems associated with specialization could be solved by a better supervision of medical practice. Therefore they once more stressed the importance of the establishment of a disciplinary council, the Order of Physicians. Discussions about the respective role of general practitioners and specialists were altogether absent.