[4] The episcopal see was originally at Santa Sabina church in Marruvium, but, as this place was isolated and therefore insecure, Pope Gregory XIII permitted, in 1580, the removal of the bishop's residence to Pescina, where the cathedral was completed in 1596.

On account of his justice and of his severity in that office, he was imprisoned by Pietro Colonna, but Pope Paschal II made him a cardinal, and bishop of his native town.

[9] At the general council held in the Lateran by Pope Victor II, on 18 April 1057, however, the decisions of Benedict IX were reversed,[10] and the diocese of Marsi reunited in its original form.

[12] On 25 February 1114, Pope Paschal II issued a bull, "Sicut iniusta poscentibus," confirming for Bishop Berardus all of the parish boundaries and enumerating all of his privileges and rights.

[13] Pope Gregory XIII published the bull "In suprema dignitatis" on 1 January 1580, in response to petitions from Bishop Matthew, leaders, and citizens of the civitas Marsorum, who pointed out that for more than forty years the city had been devastated, the victim of wars.

[14] He granted their requests, and transferred the episcopal seat, the canons, all the benefices, and other diocesan apparatus to the church of Santa Maria delle Grazie in Pescina.

He was succeeded by Pompeo Gallosio, the Provost of Celano, for five months in 1606, until Bishop Peretti was finally released in the middle of the year.

On his return to the diocese, he preferred to stay at the family palazzo in Celano rather than in the less congenial Pescina, where the episcopal palace was in a run-down condition.

[25] Bishop Camillo Giovanni Rossi (1805–1818) held a diocesan synod on 10–12 September 1815 in the cathedral of Santa Maria delle Grazie.

In the case of the diocese of Marsi, it was decided that the papal Curia would continue to use the official name Dioecesis Marsorum, but that in the Italian vernacular it should be referred to as Diocesi di Avezzano.