Traditionally, people were recognized as being dead using cardio-respiratory criteria: individuals who had permanently stopped breathing and whose heart had permanently stopped beating were dead. Technological developments in the middle of the twentieth century and the advent of the intensive care unit made it possible to sustain cardio-respiratory and other functions in patients with severe brain injury who previously would have lost such functions permanently shortly after sustaining a brain injury. What could and should physicians caring for such patients do? Significant advances in human organ transplantation also played direct and indirect roles in discussions regarding the care of such patients. Because successful transplantation requires that organs be removed from cadavers shortly after death to avoid organ damage due to loss of oxygen, there has been keen interest in knowing precisely when people are dead so that organs could be removed. Criteria for declaring death using neurological criteria developed, and today a whole brain definition of death is widely used and recognized by all 50 states in the United States as an acceptable way to determine death. We explore the ongoing debate over definitions of death, particularly over brain death or death determined using neurological criteria, and the relationship between definitions of death and organ transplantation.