Abstract
This article deals with the activity of Bishop Áron Márton of Alba Iulia in the second half of the twentieth century, during the restrictions imposed by the Communist authorities. Like the Greek-Catholic prelates, the Roman-Catholic bishop of Alba Iulia was impeded by the authorities from participating to Vatican II council. He was imprisoned for a while. Even after he was freed from jail, he was condemned indefinitely to house arrest. Nevertheless, after the Communist authorities normalized diplomatic relationship with Vatican at the end of 1960s, the bishop was allowed to visit Rome. In spite of the constraints, Bishop Áron Márton’ skilful and courageous measures succeeded to apply the most important decisions of Vatican II council, regarding the instruction of priests, liturgical and sacrament changes, etc.. Bishop Áron Márton was favourable to the decisions of the council, influencing his priests and parishioners with his attitude.

Keywords
Áron Márton, Bishop, Council, Vatican, Alba Iulia, Diocese.