Gaudentius had studied under Philastrius, and was a preacher in Italy and the Middle East. When Philastrius died around 387, the people of Brescia elected Gaudentius as bishop –evidently against his will. He was on pilgrimage to Jerusalem when Philastrius had died. The Catholic Encyclopedia states that “the people of Brescia bound themselves by an oath that they would accept no other bishop than Gaudentius; and St. Ambrose and other neighboring prelates, in consequence, obliged him to return, though against his will. The Eastern bishops also threatened to refuse him Communion if he did not obey.”
He was consecrated by Saint Ambrose in 387. A record of the discourse made by Gaudentius on the occasion of his consecration survives. Gaudentius reported upon his consecration that he had brought back with him from the Holy Land relics of Saint John the Baptist, the Apostles, relics of saints from Milan, and of the Forty Martyrs of Sebaste. The nieces of Saint Basil had given him the relics of the Forty Martyrs at Caesarea in Cappadocia.
He deposited these relics in a basilica that he named Concilium Sanctorum, and wrote a sermon upon its dedication.