This volume contains an edition and facing English translation of Explanation of the Divine Temple and 'On the Sacred Liturgy,' the two commentaries on the pontifical (hierarchal) Byzantine Divine Liturgy by St. Symeon of Thessalonika (?1429). This edition is based on MS Zagora 23, which contains extensive corrections and additions apparently added to the text by the author himself. The book opens with a historical and theological foreword on liturgical commentaries and mystagogy by Archimandrite Robert Taft. The introduction surveys the life and career of St. Symeon, analyzes the structure and theology of the commentaries, and concludes with an account of technical and editorial questions. The index includes references to names, places, and topics in Symeon's text and in the introduction and traces key terms in the commentaries in both Greek and English.