Once imperial favour made it safe, the Chi-Rho spread rapidly across the fourth-century Christian world, on coins, sarcophagi, lamps, mosaics and the apses of churches, often flanked by the Greek letters alpha and omega, the first and the last of the Book of Revelation, and sometimes enclosed in a victory wreath. It frequently stands beside the tau-rho staurogram and the iota-chi monogram. As Christianity became the religion of empire the monogram carried a triumphal rather than a suffering sense, akin to the jewelled cross of the same period.
In later Western use it survives especially in manuscript ornament: the Chi-Rho page of the Book of Kells, filling an entire folio with interlace grown out of the monogram's two letters, is among the most celebrated single pages in all of Insular art, and the same device recurs at smaller scale across Carolingian and Ottonian gospel books as the conventional way to mark the opening of Matthew's genealogy of Christ, the point in the text where the name Christos first occurs. The monogram remains in active liturgical use: it appears stamped on paschal candles blessed at the Easter Vigil in the Catholic and many Anglican rites, flanked there by alpha, omega and the numerals of the current year, a modern continuation of the same abbreviating impulse that first put chi and rho together in a scribe's hand centuries before Constantine gave it an empire.