"Mystiques, Etat et Societe" considers the history of a mystical Muslim brotherhood, the Halvetis, in southeastern Europe since its introduction to the region. It immediately became the most widespread of all the brotherhoods in this area. This study is based on fieldwork and diverse written sources, including unedited manuscripts. The text examines: the role of the Halvetis in the spread of the ideology propagated by the Ottoman political authorities ("Sunnitization", conquests, colonization, Islamization) and in the uniting of the Muslim populations; the expansion and social rooting of the brotherhood; and its development in the post-Ottoman period. This study clarifies important phenomena for understanding both Balkan and Ottoman history, and the working of mystical Muslim brotherhoods themselves.