Brain death (BD) means the irreversible loss of all brain and brain stem functions and physiopathologically the cessation of intracranial circulation. BD is a clinical diagnosis that can be made with various clinical tests. However, in order for BD to be definitely established, clinical tests performed initially need to be repeated after 24 h or to be confirmed by corroboratory tests. In addition, the obligation to confirm BD using corroboratory tests varies in current guidelines from country to country but has been eliminated except for certain specific circumstances. However, considering the adverse effects on patients awaiting donor and organ donations of the time lapse between initial and repeat tests in order to confirm BD, more rapid confirmation of definite BD is commonly made using corroboratory tests.