This chapter provides definition, pathophysiology, injury severity markers, symptoms, cognition, structural and functional neuroimaging and return-to-play decision making and prevention of concussion. It explains about multiple concussions, concussive convulsions and chronic traumatic encephalopathy(CTE). International Symposia on Concussion in Sport were held and concussion experts from around the world met to discuss specific issues related to the injury. Concussion can be considered an injury at the mild end of the mild traumatic brain injury (MTBI) continuum with loss of consciousness (LOC) and post-traumatic amnesia being considerably briefer in duration. Concussion in athletes is typically produced by acceleration/deceleration forces. Concussions can have an adverse effect on balance during the early stages of recovery; thus, balance testing can be used to track recovery. CTE was historically described as a progressive neurodegenerative syndrome occurring in boxers who had a significant history in the sport.