Abstract : If the critical reading of dominant media presents itself as a combat where the altermondialist movement must be active, the strategy of resistance to the diktats of the dominant ideologies also passes by the appropriation of most recent communication and information technologies and the creation of alternative media defending of the values other than those of the market, making it possible the social movements to reach a certain media emancipation. The initiatives going in this direction multiplied these last years, revealing the emergence of sociotechnic devices carried by an informational militancy whose existence even is due to the committal for trial of journalistic constructions and to the production of autonomous representations of the movement. One can undoubtedly advance the idea of the construction of a transnational media repertory suitable for the altermondialist movement, a media public space multiform, made communities of action and varied spaces of representation, and in which dimensions at the same time local, national and international interpenetrate in a strong way. Without having the means of advancing that such public spaces (such that they are given to see through case of Attac-information or other initiatives) contribute indeed to the mobilization of the action, one can undoubtedly more easily think than their existence at least makes it possible to ensure a better representation of the interests of the altermondialists fights and to contribute to construction of the symbolic system of the identities of a movement in full growth, beyond the militant circles which work directly with its construction. During former work, we defended the idea that, overall, these "new" public spaces were the place of a rebuilding of certain figures of social and political criticism and that they were carrying speech contradicting the idea of a depoliticization and an orientation towards testimony compassionnel of the public forms of expression. Although last research which we undertook (in particular the case of Attac-information) does not contradict the more marked character of the repertories of the public word, the attention which we carried here to the effective operation of the one of these informational spaces, leads us however to specify that the relative toughening of spaces of representation, does not attest to in no case in an automatic way of an ideological strengthening of the communities of action which carry them.