Apostolic Constitutions, late-4th-century compilation, in eight books, of administrative canons for the clergy and the laity and of guides for worship. They were supposed to be works of the apostles, but actually included the greater part of the Didascalia Apostolorum, a lost Greek treatise of 3d-century origin, most of the Didache, and fragments from Hippolytus and Papias. The work concludes with a collection of 85 moral and liturgical canons known as the "Apostolic Canons," a portion of which became part of canon law of the Western Church. The work is thought to be of Syrian origin. The whole is a valuable primary source on early church history and practice.