This thesis describes, analyses and compares changes in the practice of human resource management (HRM), the roles of human resource departments (HRD) and management models in companies in Belgium, France (partially) and Chile by highlighting the similarities and differences. This is therefore an international comparative study. The study is carried out using a contextualist analytical approach. It answers the question: what are the changes in HRM practice, the roles of HRD and the management models in social organisations in different contexts? It uses theoretical models (“typical ideals”) to analyse reality, while drawing from writers such as Mintzberg, Pichault and Nizet, Crozier, Crouch, Ulrich, Pettigrew. With regard to management, the study resorts to classical, instrumental and political models. As regards human resource management (HRM), it is based on objective, conventionalist and individualised models. In the human resource department (HRD), the models are those of administrative officer, operational expert and strategic partner. The changes do not only result from a decision-making process dictated mechanically by contextual factors but more particularly from complex interaction and the balance of power among the actors concerned who use the contextual elements to advance their own interests. Amongst the most relevant developments which bear similar characteristics, one can cite: 1.- a significant increase in the use of management methods specific to the instrumental or “Californian” model, 2.- more extensive use of individual competencies in HRM practices , and 3.- a significant reduction in the size of the HRD and, notably, in the profile of administrative officer of the HRD. As regards the differences found in the various contexts, one can highlight the fact that: 1.- In the Belgian and French models, the dominant managerial model remains political management. On the other hand, in the Chilean model, the Californian management model has become clearly dominant. 2.- In Belgium and France, the ...