De mysterio missae has received relatively little recent scholarly attention from liturgical historians and theologians. Interest in the text has either focused on questions surrounding its authenticity or on a few short passages in which Albertus Magnus (1200-1280) speaks out against specific allegorical interpretations of ritual acts or prayers. Although the authenticity of the text is no longer in any real doubt, due to these scholarly foci and the lack of a critically edited version of the text, De mysterio missae has remained one of Albertus Magnus' lesser-known works.  Made up of three tractatus which conform to the contours of the liturgy, De mysterio missae offers Albertus's vision of the Mass and its place in the economy of salvation. He embraces the view put forth by the earlier theologian and philosopher, pseudo-Dionysius the Areopagite. Through the Sacrament of the Eucharist and the ritual that leads up to and comes after its confection, according to this view, God inclines to us and draws us back up to him, imparting as much divinizing grace to each participant as s/he is able to receive. This divinization process involves not only the progression of God's moving out and returning to himself but also entails each individual being purified, illuminated, and perfected.  This dissertation provides a thorough study of the text including analyses of its formal, structural, and literary aspects, exposition of its liturgical and theological content. In addition, it contains a comparison of De mysterio missae with liturgical commentaries by Innocent III, William of Melitona, Hugh of St. Cher, and Guerric of St. Quentin; Innocent III's commentary was extremely influential on Albertus' own and that of others; those written by the other three of these demonstrates its relationship to the work of fellow thirteenth-century mendicant theologians. Each of the above-described chapters demonstrate the intellectual contribution Albertus has made with De mysterio missae and its interpretation of the liturgy, as a theological treatise written within the context of the thirteenth century commentary tradition.