Brain death, whether it be brain stem death in the UK, or whole-brain death in the USA, is a prerequisite for heart-beating organ donation. Understanding how brain death is perceived by family members approached about organ donation, its significance to them, and if it is accepted by them, are, therefore, important issues to explore as biomedicine expands the range of end of life technologies that blur the demarcation between life and death. To explore the concept of brain stem death and its meaning to family members the following research questions were posed: (i) what does the diagnosis of death based on brain stem testing mean to bereaved family members who have been approached and asked to consider a donation from a deceased relative, and (ii) how do family members understand the concept of brain stem death? To address these research questions, a secondary analysis of 28 interviews sorted from two primary datasets was carried out. The primary datasets contained longitudinal and cross-sectional interviews carried out in the UK with family members who had been approached about organ donation and agreed to donate their relatives' organs. Data analysis was guided by constructionist grounded theory method and resulted in the theory of Paradoxical Death. In this process, family members and health professionals engage in a series of practical and psychological activities aimed at rationalising real or potential emotional and cognitive conflict resulting from a brain-based diagnosis of death, whilst faced with the physical image of a functioning body. Rationalising emotional and cognitive conflict is how family members and health professionals appeared to process this paradoxical death, a death that is contrary to conventional opinion.