Brain death is diagnosed in the minority of patients with acute severe brain injury. Guidelines have been developed in many countries in the world and physicians usually work through a set of criteria. The clinical evaluation starts with determination of futility of any medical or surgical intervention and an unmistakable certainty that the underlying diagnosis is correct. The actual neurologic evaluation in a patient suspected of being brain dead requires 25 tests and verifications. Brain death determination demands perfect diagnostic accuracy and thus requires skill and expertise. The overriding principle is simple: establish cause, exclude confounders, determine futility of interventions, examine brainstem reflexes, and test for apnea. In this review, the author revisits the American Academy of Neurology guidelines, and examines the details behind the guidelines. The 2010 guidelines have eliminated unnecessary tests and observation delays, and maintain a principle of simplicity.