Sextus Julius Africanus, who visited Alexandria in the Bishoprice of Demetrius, places his accession as eleventh bishop from Mark in the tenth year of Roman Emperor Commodus; Eusebius of Caesarea places it in the tenth year of Septimius Severus.

[3] According to the Coptic Synaxarium, a biographical collection of the Church's saints, the ailing Patriarch Julian had a vision informing him that his successor would visit him, with a cluster of grapes, while out of season at that time of year.

Bishop Demetrius was eager to establish a fixed calendar for church fasts and feast days.

When the Emperor Caracalla sacked Alexandria in 215 AD, Origen fled to Caesarea, where the Palestinean bishops requested him to give sermons.

Bishops Alexander of Jerusalem and Theoctistus of Caesarea wrote in his defense and mentioned precedents for laymen to give sermons, but despite their efforts Demetrius recalled Origen.