The most common head injury in sports is concussion and experiencing multiple concussions in a short period of time sometimes can cause severe brain damage. In this paper, we investigate severe brain damage due to repeated head injury in sports and discuss the pathophysiology of repeated sports injury. The majority of these severe cases are usually male adolescents or young adults that suffer a second head injury before they have recovered from the first head injury. All cases that could be confirmed by brain CT scan after the second injury revealed brain swelling associated with a thin subdural hematoma. We suggested that the existence of subdural hematoma is one of the major causes of brain swelling after repeated head injury in sports. Since repeated concussions occurring within a short period may have a risk for severe brain damage, the diagnosis for initial cerebral concussion should be done appropriately. To prevent catastrophic brain damage, the player who suffered from concussion should not engage in any sports before recovery. The american Academy of Neurology and Colorado Medical Society set a guideline to return to play after cerebral concussion. An international conference on concussion in sports was held at Prague in 2004. The summary and agreement of this meeting was published and the Sports Concussion Assessment Tool (SCAT) was introduced to treat sports-related concussion. In addition, a number of computerized cognitive assessment tests and test batteries have been developed to allow athletes to return to play. It is important that coaches, as well as players and trainers, understand the medical issues involved in concussion.