• Most major U.S. professional sports and the National Collegiate Athletic Association (NCAA) have adopted concussion policies. Current National Football League and NCAA guidelines do not permit an athlete with a concussion to return to play on the same day as the injury. No adolescent or high-school athletes with a concussion should be allowed to return to play on the same day regardless of severity. • Loss of consciousness is uncommon with concussion. • Acute concussion symptoms are generally self-limited, and most symptoms typically resolve within two weeks. Concussion risk and severity may be affected by age, sex, and genetic predisposition. • Athletes with a concussion should rest physically and cognitively until symptoms have resolved at rest and with exertion. Rehabilitation following concussion progresses through a stepwise graded fashion. • Neuropsychological testing can provide objective data on an athlete after a concussion. However, it alone cannot be used to diagnose a concussion or determine when an athlete is allowed to return to play. • Retirement from contact or collision sports may be necessary for an athlete who has sustained multiple concussions or has a history of prolonged symptoms after concussions. • Long-term effects of concussions are still relatively unknown, and further research is required to offer guidance for athletes of all levels.