Following the example of Augustine of Hippo, he is said to have organized his cathedral clergy into a "congregation," devoting a great part of their time to social exercises of asceticism.

He held the rank of metropolitan bishop of Vienne and Narbonne, and attempted to exercise the sort of primacy over the church of south Gaul, which seemed implied in the vicariate granted to his predecessor Patroclus of Arles (417).

An appeal was made to Rome, and Pope Leo I used it, in 444, to extinguish the Gallican vicariate headed by Hilary, thus depriving him of his rights to consecrate bishops, call synods, or oversee the church in the province.

During his lifetime Hilary had a great reputation for learning and eloquence as well as for piety; his extant works (Vita S. Honorati Arelatensis episcopi and Metrum in Genesin) compare favourably with any similar literary productions of that period.

[3] A poem, De providentia, usually included among the writings of Prosper of Aquitaine, is sometimes attributed to Hilary of Arles.