Neuropsychological performance, magnetic resonance imaging (MRI) and electroencephalography (EEG) were investigated in 12 consecutive patients with very mild traumatic brain injury (MTBI) (Glasgow coma score 15) within 24 hours and 6 weeks after injury. The data were compared to 14 control subjects. There was a significant impairment in neuropsychological performance (verbal memory, arithmetic abilities and psychomotor reaction time) at onset and after 6 weeks, whereas verbal fluency and non-verbal memory test revealed no significant differences matching the control values. In MRI scans, three patients showed traumatic lesions (slight epidural haematoma, haemorrhagic contusions and white matter lesions indicating diffuse axonal injury). In the EEG recordings, no generalized slowing or focal changes were found. Structural and functional impairment can be identified using neuroimaging and neuropsychological examination, even in very MTBI patients.