The most common head injury in sports is concussion. Athletes who sustain a prolonged loss of consciousness should be transported immediately to a hospital for further evaluation. Assessment of less severe injuries should include a thorough neurologic examination. The duration of symptoms and the presence or absence of post-traumatic amnesia and loss of consciousness should be noted. To avoid premature return to play, a good understanding of the possible hazards is important. Potential hazards of premature return to play include the possibility of death from second-impact syndrome, permanent neurologic impairment from cumulative trauma, and the postconcussion syndrome.