Four hundred patients (221 young, 179 adults) with a cerebral concussion (317 minor, 83 mild) were examined within 48 hours after blunt head injury. In mild concussions there is a threefold homogeneous increase in the different EEG and BEP abnormalities compared to minor concussions. In the younger group EEG abnormalities are far more frequent than BEP abnormalities. An early EEG and/or BEP could be more useful than an EEG and/or BEP in the reconvalescent phase. Follow-up studies will have to prove their value in determining the risk of later posttraumatic epilepsy.