ACOLIT is an authority list of catholic authors (persons or corporate bodies) and of liturgical and religious anonymus works. ACOLIT formulates catalogue entries on the basis of RICA, but also takes into account the Norme per il catalogo degli stampati of the Biblioteca Apostolica Vaticana, the AACR2R, the Regeln für die alphabetische Katalogisierung (RAK), the Reglas de catalogación, and the recommendations of IFLA. Three volumes have already been published: Bible, Catholic Church, Roman Curia, Papal State, Vatican, Popes and Antipopes (1997); Catholic religious orders (2000); Liturgical works (2003). The fourth volume is devoted to Fathers of the Church and to Western ecclesiastical Writers (II-XIII centuries). Our point of departure for this authority list are the indices in Migne Patrologia Latina, compared with indices of other authoritatives directories paper and on line (p.e., Personennamen des Mittelalters, Bibliotheca sanctorum, BISLAM: Bibliotheca scriptorum Latinorum medii recentiorisque aevi, Dictionnaire d’histoire et de géographie ecclésiastiques, VIAF). The principal lemma is the Italian form according to the language of the catalogue. The principal entry is followed by variants. For the realization of this authority list we, the editors, had to expend considerable energy in the effort to establish homogeneous forms using bibliographical sources and directories: we realize we may not have always succeeded and would be happy to receive suggestion or further information.