The acute symptoms of concussion provide the basis for assessment, classification, and ultimately, management of this common problem in sport. The only concussive symptoms that have been scientifically validated are loss of consciousness, headache, dizziness, nausea, blurred vision, attentional deficit, and memory loss. Although many symptoms have been anecdotally attributed to concussive injury, their clinical significance is unknown. An evidence-based analysis of concussive symptoms and their prognostic significance can aid physicians who must make management and return-to-play decisions.