The natural death of humans begins with ceasing of the heartbeat and breathing, and then other organs will lose their lives. This phenomenon has been accepted as that of death by physicians, and Shiite and Sunni jurisprudents; however, the main doubts about human death are related to the brain cells as in such a state, the heart has its activity, but human life is limited only to a vegetative life and there is no way for returning to human life, and only with the help of medical devices, the life of other organs can be maintained for a period of time. It is important to identify the beginning of the death stage of a patient with brain death in order to enforce the jurisprudential and legal rulings applicable to the deceased; therefore, in this research, the question where such a person is dead or alive was analyzed in two areas of religion and medicine. Examining the reasons behind the views leads to this result that, from the viewpoint of physicians, a patient with brain death is considered dead, but according to the opinion of the Shiite and Sunnite jurisprudents and the common law, the patient with brain death is considered alive; and Islamic jurisprudential and legal rulings applicable to the deceased will not be applicable to such a person until the real death of such a person is established.