[2][3] Acerenza was certainly an episcopal see in the course of the fifth century, for in 499 we meet with the name of its first known bishop, Justus, in the Acts of the Roman Synod of that year.

[4] Acerenza was in early imperial times a populous and important town, and a bulwark of the territory of Lucania and Apulia.

An Archbishop of Acerenza (Giraldus) appears in 1063 in an act of donation of Robert Guiscard to the monastery of the Santissima Trinità in Venosa.

For a few years after 968 Acerenza adopted the Greek Rite in consequence of an order of the Byzantine Emperor Nicephorus Phocas (963-969), whereby it was made one of five suffragans of the archdiocese of Otranto, and compelled to acknowledge the jurisdiction of the Patriarch of Constantinople.

to be a portrait-bust of Julian the Apostate, though others maintain that it is a bust of the Emperor Frederick II, after the manner of the sculptors of the Antonine age.