Sports-related concussion has gained increased prominence, in part due to media coverage of several well-known athletes who have died from consequences of chronic traumatic encephalopathy (CTE). CTE was first described by Martland in 1928 as a syndrome seen in boxers who had experienced significant head trauma from repeated blows. The classic symptoms of impaired cognition, mood, behavior, and motor skills also have been reported in professional football players, and in 2005, the histopathological findings of CTE were first reported in a former National Football League (NFL) player. These finding were similar to Alzheimer's disease in some ways but differed in critical areas such as a predominance of tau protein deposition over amyloid. The pathophysiology is still unknown but involves a history of repeated concussive and subconcussive blows and then a lag period before CTE symptoms become evident. The involvement of excitotoxic amino acids and abnormal microglial activation remain speculative. Early identification and prevention of this disease by reducing repeated blows to the head has become a critical focus of current research.