St.-Denis is celebrated as the birthplace of Gothic architecture, the place of origin for the largest vernacular history project in the Middle Ages, the repository for one of the richest treasuries in medieval Europe and the most important royal necropolis in the history of France. This publication makes available a complete edition of the richest liturgical manuscript of St.-Denis in existence. Paris, Bibliothèque Mazarine 526 is the single most important resource for reconstructing worship at the royal abbey in the twelfth and thirteenth centuries. Reflecting the work of Abbot Suger ( d. 1151) this codex, written c. 1234, documents the state of worship in the hybrid Gothic-Carolingian church which existed until the late thirteenth century. Beginning with First Vespers of the First Sunday of Advent and continuing through the entire temporal cycle and eleven of twelve months of the sanctoral cycle, this manuscript details the places, ministers, texts, artifacts, bells, vesture, processions and other rubrics which allow this liturgy to be thoroughly examined. This edition is complemented by extensive inices which allow access to all of the almost 5000 liturgical texts contained in the manuscript. An accompanying study of the manuscript, introduced by an essey on the history of St.-Denis, analyzes three important aspects of this worship: the structure of the offices, the calendar of saints and anniversaries, and the spatial deployment of the worship.