Together with his deacons Socius and Festus, and his lector Desiderius, Januarius, bishop of Beneventum, was subjected to most atrocious torturing during the Diocletian persecution (about 304). Nevertheless, with God's aid they were preserved unmaimed. The wild animals let loose upon them would not attack. Beheaded at Puteoli, their bodies were reverently interred in the neighboring cities. Eventually the remains of St. Januarius became the prized possession of the city of Naples.

"Even to the present time the blood of the saint that is preserved in a glass vial will become fluid shortly after it is brought close to the head of the saint; then it bubbles up in a remarkable manner, as if it had just been shed" (Breviary). Cardinal Schuster makes this statement in his Liber Sacramentorum (vol. 8, p. 233): "The author has seen the marvel of the blood liquefaction at closest range and can give witness to the fact. Taking into consideration all the scientific investigations that have been made, he would say that a natural explanation of the phenomena does not seem possible."

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