The authors revied cardio-vascular physiologics criteria in order to valid a patient with cerebral death for a non mutilant therapeutic study conform to ethical standards as set out in the Declaration of Helsinki. Various tests are discussed. it is necessary to ensure homeostasis and to know if adrenergic receptors are active. The principal problem is the vascular effects of cerebral death on local circulations. It is concluded that it is difficult to use a patient with irreversible coma as a biological model.