In this paper the author, the Regent of the Apostolic Penitentiary, has illustrated the oldest Dicastery of the Roman Curia, which is the Apostolic Penitentiary, its structure, competency, activities and the method of its daily work, as well as the treatment of cases of conscience which, because of their gravity, are reserved to the Apostolic See.It was pointed out that it is the Tribunal of Mercy at the service of the Church, and that based on the experience of centuries of Church history, it can be proven that everything pertaining to the internal forum in the Church is of inestimable value. The mission of the Church is the salvation of souls. In this mission the Tribunal of the Apostolic Penitentiary enters in a most special way. It is t...