Brain death, the colloquial term for the determination of human death by showing the irreversible cessation of the clinical functions of the brain, has been practiced since the 1960s and is growing in acceptance throughout the world. Of the three concepts of brain death--the whole-brain formulation, the brain stem formulation, and the higher brain formulation--the whole-brain formulation is accepted and practiced most widely. There is a rigorous conceptual basis for regarding whole-brain death as human death based on the biophilosophical concept of the loss of the organism as a whole. The diagnosis of brain death is primarily a clinical determination but laboratory tests showing the cessation of intracranial blood flow can be used to confirm the clinical diagnosis in cases in which the clinical tests cannot be fully performed or correctly interpreted. Because of evidence that some physicians fail to perform or record brain death tests properly, it is desirable to require a confirmatory test when inadequately experienced physicians conduct brain death determinations. The world's principal religions accept brain death with a few exceptions. Several scholars continue to reject brain death on conceptual grounds and urge that human death determination be based on the irreversible cessation of circulation. But despite the force of their arguments they have neither persuaded any jurisdictions to abandon brain death statutes nor convinced medical groups to change clinical practice guidelines. Other scholars who, on more pragmatic grounds, have called for the abandonment of brain death as an anachronism or an unnecessary prerequisite for multi-organ procurement, similarly have not convinced public policy makers to withdraw the dead-donor rule. Despite a few residual areas of controversy, brain death is a durable concept that has been accepted well and has formed the basis of successful public policy in diverse societies throughout the world.