Real-time head acceleration of football players during competition has been recorded by the use of a telemetry system. The individual players carry battery driven transmitters which are concealed on their equipment, while the receivers are located along the sidelines. Peak linear accelerations in excess of 1000 G's were recorded several times on individual players during one game without apparent injury. The tolerance limits for head acceleration reported in the literature may not be applicable to the football player wearing modern protective equipment.