By the end of the 1960s, Guillaumin was already interested in feminism. In 1972, analogies between the notions of race and sex were found in "L'idéologie raciste". Guillaumin was part of the group of feminists who had been working on the issue for many years. As part of this, herself and others founded the journal "Questions féministes" in 1977 (although she was not on the editorial board that inaugurated the journal), which was the source and publication organ of materialist feminism. During this time, she worked with Christine Delphy, Monique Wittig, Nicole-Claude Mathieu, Paola Tabet, Monique Plaza and Emmanuèle de Lesseps. In 1978, she published "Pratique du pouvoir et idée de nature" (in two parts), which theorized the appropriation of women through material social relations and naturalist ideology. She draws parallels between racism and sexism, and gives the name "sexing" to the appropriation of one gender class by another. In this field, Guillaumin wrote several texts for the Mouvement contre le racisme et pour l'amitié entre les peuples (MRAP) and was involved in feminist groups following on from the May 1968 civil unrest.