It is first mentioned in the Bull "Cum Certum Sit" of Pope John XIII of 26 May 979, which promoted the diocese of Beneventum to metropolitan rank, and named Ariano as a suffragan see.

In a document of October 1016, the Archpriest Petrus acts in the capacity of "rector episcopii sancte sedis Arianensis, in a suit "una cum Cicinus clericus atvocatorem predicto episcopio."

[9] Bishop Meinardus of Ariano attended the provincial synod summoned by Archbishop Milo of Benevento in March 1075.

[10] The bishops of Ariano also held the fief and the title of Barons of S. Eleuterio, certainly by 1307, and perhaps as a gift of the emperor Frederick II (d.

Bishop Orso Leone (1449–1456) had a metrical inscription placed in the episcopal palace, numbering the dead at a thousand.

The right of the king to nominate the candidate for a vacant bishopric was recognized, as in the Concordat of 1741, subject to papal confirmation (preconisation).

[23] Fra Michele Maria Caputo was a Dominican friar, born at Nardo, in the heel of the boot of Italy.

[25] He made his formal entry into the diocese on 20 February 1851, and immediately began a program of reform of the clergy.

He also undertook a reform of the staff of the diocesan seminary, replacing dead wood with priests who were in touch with modern philosophy and theology.

[26] He was a supporter of the pope's claims to universal spiritual authority, and he warmly endorsed the new doctrine of the Immaculate Conception (1854).

When he began to look closely into the episcopal income and the finances of the diocese, he discovered many cases of misappropriation of goods and properties.

Retaliation against the bishop took the form accusations lodged with higher religious and civil authorities, in particular, that he was often absent from Oppido, in the village of Piminoro, where he maintained an illicit relationship with his housekeeper.

When supporters of Garibaldi, led by General Turr, approached Ariano,[29] a conservative peasant uprising resulted in the murders of some thirty liberals.

On 20 September 1860, the Giornale officiale di Napoli published Caputo's official adherence to the new regime in Naples, which he had signed two days earlier.

On December 20, 1860, Bishop Caputo issued a pastoral letter, criticizing the closed-mindedness of seminary instruction, and invited the clergy to welcome Vittorio Emanuele, whom they proclaimed their King and who, having placed himself at the head of the nation, devoted himself to the liberation of his people.

[31] On 28 February 1861, the papal Congregation of the Council issued a formal warning to the bishop, ordering him to leave the office of Cappellano Maiore,[32] which he was holding on a temporary basis.

On 9 July 1861, he was named Cappellano Maggiore by King Victor Emmanuele II, giving him jurisdiction over royal churches and chapels as well as army chaplains, independent of the authority of the archbishop of Naples.

Based on the revisions, a set of Normae was issued on 15 November 1984, which was accompanied in the next year, on 3 June 1985, by enabling legislation.

According to the agreement, the practice of having one bishop govern two separate dioceses at the same time, aeque personaliter, was abolished.

[39] The cathedral of Ariano was dedicated to the Taking Up of the Body of the Virgin Mary into Heaven sub titulo Deiparae Virginis Assumptae.

The Collegiate Church of S. Michele Arcangelo was presided over by the bishop, who was its abbot; he governed through an appointed Vicar Curate.

[14] A diocesan synod was an irregularly held, but important, meeting of the bishop of a diocese, his clergy, and other interested parties.

(1585–1602) held a diocesan synod in 1594, in which limits were imposed on regular clergy to hear confessions, and only with written permission of the parish priest.

(1689–1696) attended the provincial synod, summoned by Cardinal Vinzenzo Maria Orsini, Archbishop of Benevento, held on 11–14 April 1693.