A controversial term first described by Saunders and Harbaugh1 in 1984, Second Impact Syndrome (SIS) consists of two events. Typically, it involves an athlete suffering post-concussive symptoms following a head injury.2 If, within several weeks, the athlete returns to play and sustains a second head injury, diffuse cerebral swelling, brain herniation, and death can occur. SIS can occur with any two events involving head trauma. While rare, it is devastating in that young, healthy patients may die within a few minutes. Emergency physicians should be aware of this syndrome and counsel patients and their parents concerning when to allow an athlete to return to play. Furthermore, we present guidelines for appropriate follow up and evaluation by a specialist when necessary.