This is an updated edition of the English translation published in 1963 based on Volume I of Le Corps Mystique du Christ: Fr. Ernest Mura's classic treatment of the doctrine of the Mystical Body of Christ originally published in French in 1934. It also features the first-ever English translation of Fr. Reginald Garrigou-Lagrange's preface found in the original French edition. The unity of the total Christ and his supernatural activity are the two aspects of the theology of the Mystical Body. Father Mura's present study limits itself to the first aspect, which is the most delicate problem of all: "You are the Body of Christ" (1 Cor. 12:27). The question of how to understand this bold assertion of St. Paul has been asked by many theologians, who, nevertheless, have not attempted to answer it; perhaps they fear that explanations which are too human may mar the beauty of the dogma of our incorporation into Christ Jesus. Hence, they do not explain wherein consists the organic and vital cohesion that makes of Jesus and ourselves a single "total Christ." Viewing the building up of the Mystical Body from the vantage point of the author's synthesis, the reader will see in it the great recapitulation in Christ, to which all the works of God are ordered for the salvation of the human race. Once the revealed truths that are most familiar to us-the notion of grace, the sacrament of baptism, the dogma of the spiritual motherhood of Mary-are seen in their relationship to the total doctrine, they take on a breadth, a supernatural beauty, and a practical significance that we did not suspect.