The manuscript Ms. Lac. 0cc. 402 from the Staatsbibliothek zu Berlin Preußischer Kulturbesitz is foremost among the sources for an understanding of the Ciscercian Divine Office in its origins and in its 12th-centmy evolution. Daring from 1132, it is the sole extant breviary known to have survived ehe massive liturgical reform carried out in the Cistercian Order under the general direction of St. Bernard and his collaborators, a reform which ended around 114 7. For ehe first time we have ehe means of knowing exactly the texts used in the Divine Office in the early days of the Order; and for the first time we have a means of identifying precisely the texts revised by Bernard and his fellow-editors. We can thus gain an insight into the mind and spirit of those responsible for the shaping up of the Order's Office.