Patients who had sustained a severe concussion of the brain more than 2 years earlier were tested in choice reaction time tasks in the laboratory in order to investigate their impaired reactive capacity. The focus of investigation was whether specific stages in the chain of the information process are affected by the injury. In addition, driving skills were measured in an instrumented car to determine if reaction time performance is predictive of car driving. In general, patients were much slower than control subjects, both in the reaction time and in the driving tasks. The results obtained in the reaction time tasks provide no conclusive evidence, however, that severe concussion of the brain affects particular stages in information processing. Reaction time tasks appear to have predictive value for the ability to drive a car.