He was imprisoned from 1960 to 1968 and meanwhile cared for the spiritual welfare of his fellow prisoners. Korec spent most of that period in Valdice, a Czech prison. There were at least 250 priests and several bishops being held: Vojtašák, Zela, Otčenášek, Hlad and Hopko. The clergymen were forced to share prison cells with some of the country's worst criminals. He later described his experiences in "Night of the Barbarians". After many petitions, he was released during a general amnesty in 1968.