Abstract: (Crisis and Episcopal Authority: The Milan Basilica Controversy of 385/386 A.D.) Posterity has hailed the 381 A.D. councils of Constantinople and Aquileia, respectively, as the formal ending to the most serious ecclesiastical crisis in the fourth century, the Arian controversy – which had long lasting impacts including in social and administrative-imperial sphere. However, Arianism was far from being defeated. Significantly, Valentinian II, the youngest scion of the Valentinian dynasty, continued to support Homoian Arianism despite the fact that both Gratian in the West and Theodosius in the East had declared themselves in favour of Nicene Christianity. The crisis escalated again when Valentinian’s court settled in Milan: Open conflict with the formidable bishop of Milan, Ambrose, the architect of the aforementioned council of Aquileia, was almost unavoidable. In the paper proposed here we shall examine this conflict from the perspective of Ambrose's epistles on the subject, ep. 10.75, 75A, and 76 (Maur. 20-21A), addressed to the emperor and Ambrose’s sister, respectively, but meant in reality to be circulated at least in northern Italy. First, we shall propose a chronology of events; next, we shall analyze the strategies through which the bishop of Milan presented this conflict to advance his own agenda of episcopal autonomy and authority. We shall argue that, through skillful rhetoric and a selective presentation of the issues at stake, Ambrose transformed what was intended to be a policy of religious tolerance into an illegitimate attack on the integrity of the faith, into a conflict between imperial and episcopal authority. The three documents represent the quintessence of the Ambrosian ideology of episcopal authority, the only body capable of judging in matters of religion.