Understanding the precise diagnosis of brain death is of importance to the neurointensivist. This chapter presents a case study of a 21-year-old male who was brought to the neurosurgical intensive care unit (ICU) following evacuation of a large right-sided traumatic subdural hematoma. The most common primary neurologic diseases that result in brain death are traumatic brain injury and subarachnoid hemorrhage. Several other conditions including hypoxic-ischemic injury and fulminant hepatic failure can result in brain death. A clinical examination is performed to confirm the patient's comatose state and to evaluate brain stem reflexes. Confirmatory testing is useful when a full clinical evaluation cannot be performed, such as in the patient with severe facial and orbital injury and patients in coma from long-acting medications such as pentobarbital. The key impetus to the accurate and timely diagnosis of brain death is the critical shortage of organs available for transplantation.