This review article presents evidence from the current literature on the epidemiology and pathophysiology of concussion. The recent epidemiologic data for a variety of sports are presented relevant to the general population, and professional, college, and high school athletics. The evidence for the pathophysiology of head injury is presented using a mixture of current animal and human studies. A brief discussion on the benefits and limitations of the evidence is offered for the both the epidemiology and pathophysiology of concussion, and how it relates to current treatment options.