This article analyzes the demonstration organized in Montevideo on the 26th of September of 1968, by women who would later constitute the “Feminine Movement for Justice and Social Peace” (Movimiento Femenino por la Justicia y la Paz Social). For this purpose, the article builds on the Political Sociology and Political Science studies of social movements ―especially the framing theory―, as well as on studies which have analyzed women’s movements in 20th Century Latin America. The article concludes that the activists made a strategic use of the dominant values and beliefs existent in the cultural stock about women’s role. These were articulated in an interpretative frame which achieved the successful mobilization of new adherents, the spectators’ support and the press’s sympathy, through a frame alignment process. It also avoided police repression successfully, in an authoritarian context where it was expected that the law and order forces would unleash their violence against any expression of opposition to the government. Finally, taking into account that social movements contribute to enrich the cultural stock and repertoire of protest from one protest cycle to the next, we propose that this demonstration was one of the first ones to use silence as a form of protest associated with denouncing repressive actions of state authoritarianism in the Southern Cone.