This article examines relationships between Catholic and Orthodox Christians in the Grand Duchy of Lithuania at the turn of the fifteenth and sixteenth centuries. It stresses the robust policies of Catholic and Orthodox prelates and nobles towards one another and especially towards the Unionist Ruthenians, who sought to maintain their liturgical and hierarchical identity while recognising the primacy of the bishop of Rome. By contrast in personal situations Catholics and Orthodox were willing to cooperate on practical matters (usually concerning family property or community business). In Vilnius victories over national enemies (Tatar or Muscovite) were celebrated in monumental architecture by both communities. Evidence from consistory courts in Lutsk and Gniezno, and ecclesiastical emoluments in the Diocese of Vilnius reveal cooperation between both communities at a family and parish level could exist.