Fifteen whiplash patients (Whiplash) were compared with 10 patients who had documented moderate-to-severe head injury (Mod-Sev), and with 24 patients who had chronic pain syndrome (CPS) and no history of head injury on two tests of mental efficiency considered highly sensitive to and specific for the subtle effects of brain trauma. All 3 groups, assessed 4 years after onset in a teaching hospital setting were matched for age, education, and IQ