[1][2] Tradition holds that during his papacy he determined the various prerogatives of the clergy and defined the grades of the ecclesiastical hierarchy.

Hyginus instituted godparents at baptism to assist the baptised during their Christian life.

[3] Irenaeus says that the gnostic Valentinus came to Rome in Hyginus' time, remaining there until Anicetus became pontiff.

[5] Cerdo, another Gnostic and predecessor of Marcion of Sinope, also lived at Rome in the reign of Hyginus; by confessing his errors and recanting, he succeeded in obtaining readmission into the Church but eventually fell back into heresy and was expelled from the Church.

[6][7][8][9][10] The Liber Pontificalis also relates that this pope organized the hierarchy and established the order of ecclesiastical precedence (Hic clerum composuit et distribuit gradus).