The Monastery in Supraśl was founded as an Orthodox one in the late fifteenthcentury. Initially the monks opposed the Union. The Monastery subordinated to theuniate rules in 1635, it then became one of the most significant Basilian centers in theRepublic of Poland. Over time, the Basilians increasingly succumbed to Romanizationand Polonization. Consequently, Latin altars (main and side ones), pulpit, confessional,stoup, instrumental organs and Latin devotional articles were installed in the SupraślOrthodox Monastery. The restitution of the Orthodox Church was preceded by severalyears of preparation. One of the taken measures was the opening of a school in 1834in Supraśl that provided education in the spirit of sympathy for Orthodoxy. The changesto the interior of the Orthodox Church in Supraśl involved the decoration of the altaraccording to the Eastern Greek rite, the removal of the side altars and the prohibitionof instrumental music. Due to the preserved iconostasis the church was quickly adaptedfor the needs to celebrate the liturgy according to the Eastern Greek rite; the choirwas created by the students from the local school. In 1828, the Basilians who camefrom the Latin rite were allowed to return to it. Thirty four monks left the Monasteryin Supraśl, and only eight remained. The Basilian resistance against the restitution of theOrthodox Church was the result of their Romanization and Polonization. In contrast,the position taken by the Basilians from Supraśl reflected the attitude of their superior,Nikodem Marcinowski.