Brainstem Death (BSD) is defined as the complete loss of brain function, including involuntary activity necessary to sustain life. Currently, BSD is used as an indicator of legal death in many countries, but it is defined inconsistently.

The diagnosis of BSD implies that the evidence of the complete and irreversible cessation of brainstem and cerebral function, including the capacity for respiratory, brainstem, and vegetative activities, but substantial variation persists in the diagnostic criteria among different centers and countries. The aim of this chapter is to review and discuss the criteria, including clinical examination, instrumental tests, as well as ethical considerations of BSD, highlighting the challenges that the clinicians have to face in the management and diagnosis of BSD.