In 1980, the Uniform Determination of Death Act (UDDA) defined death as “(1) irreversible cessation of circulatory and respiratory functions, or (2) irreversible cessation of all functions of the entire brain, including the brain stem ... in accordance with accepted medical standards.” Interpreting the UDDA definition and applying neurological criteria for diagnosing brain death sound straightforward. Brain death is, however, socially situated, not observer independent, and fraught with uncertainty and ambiguity. This issue investigates some of the ethical, cultural, and legal complexities of one of medicine’s most critical tasks: being sharp and sure about who is alive and who is dead.