Pronouncing the death of a man is essentially connected with the question about the moral limits of reanimation actions and about taking tissues and organs from human corpses. As medicine developed it was decided that the proper criterion of the death of a man is his cerebral death. However, acceptance of this criterion arouses controversies and raises objections. The author of the article shows the contemporary development of this method of pronouncing a man dead, the main reasons for objections and the stand taken by the Church. In the further part he shows the significance of the brain as the factor integrating the man’s living processes. He does it from the perspective of the respiratory, circulatory, nervous and endocrinological systems. On the other hand, he stresses that along with the death of the brain disintegration of the human person begins. Disintegration of this unity on the biological level reveals the “separation” of the body and the soul as the unifying principle that has already happened; that is, it reveals the man’s death that has already taken place.