[ENG] This research embarks upon a study of anarchism during the Second Republic and the Spanish Civil War, while it also falls within the framework of the latest and most important historiographic contributions to this subject. It examines the distinction between anarchist militancy and membership in the Single Unions of the National Confederation of Labour (CNT); the decisive and highly significant ties between the members and the local and regional spheres, especially in the Catalan-speaking countries and even Spain-wide; the role played by the press in the movement, which set great store by their ideological aversion to politics and simultaneously the meaning that the so-called libertarian groupism had to the FAI members, as well as to the members and anarcho-syndicalist leaders of the Single Unions. Finally, the study upholds that the anarcho-syndicalist leaders and/or anarchists belonged to affinity groups that were defined according to the jobs they assigned themselves, but with the assumption that they could join or belong to more than one group according to militant friendships and specialisations, which could be strictly union-related and could also include anarchist or open cultural action the latter including theatre, newspapers and infra-littérature. However, it should be noted that the heterogeneity of the forms of membership did not imply the existence of numerous anarchisms, since unity was ensured through varied forms of solidarity and coordination, and even through the so-called honour trials.