The clinical validity of a standardized assessment of concussion in high school football players was confirmed at the Rehabilitation Institute of Chicago, and Northwestern University Medical School, Chicago, IL. A sideline examination, designed according to Colorado and AAN guidelines, and involving orientation in time, immediate memory for words, concentration for repeating digits and months, and delayed recall for words, was administered by athletic trainers to 141 non-injured players and 6 who suffered concussion. The concussed players as a group scored significantly below the controls and below their own baseline performance. Learning and delayed recall of a 5-item word list differentiated those concussed from controls. [1]