This article has for its object the discourse of leaders of community associations (Italian, Jewish, Haitian and Lebanese) in the Montreal region bearing on the national question. These leaders are implicated in social and political action and contribute to the definition of particular identities and make demands based on ethnicity. This social construction of ethnicity and the political mobilisation based on ethnicity is part of the special context in Quebec marked by the national question. The discourse is analysed in reference to three themes: the linguistic question, identity references, political orientations. The interpretation bears on the theoretical reflexion on ethnicity as a political category for action, on the analysis made of the role of the state regarding the gestion of ethnicity in the Canadian and Quebecois contexts and on the relations of force between them.