Brief account of his pontificate, from "Popes Through the Ages" by Joseph Brusher.

After a vacancy in office following the death of Pope St. Marcellinus, was elected to the papacy in 308. Fairly lengthy biographical article in the Catholic Encyclopedia.

Brief biography paints St. Marcellus I as a rigorist who refused to accept the penitence of the lapsed, and says that Christian Rome rioted against him.