Clinical quantification of mild traumatic brain injury (MTBI) patients should be based on Glasgow coma scale (GCS) score, duration of loss of consciousness (LOC) and post-traumatic amnesia (PTA). In addition, a short practicable neuropsychological test might be useful in detecting minor memory and attentional deficits. MRI appears to be the most sensitive imaging method for assessing MTBI so far, but information regarding a visualized lesion is not usually utilized in the classification of MTBI. Magnetic resonance imaging (MRI) should, therefore, play a major role in any MTBI classification scheme. An appropriate MRI protocol has to be chosen using at least T1 weighted, T2 weighted, proton density and gradient-echo (GRE) sequence images, all in at least two planes, in order to detect and classify all lesions precisely. Owing to the fact that acute lesions may be missed, it is advisable to perform MRI in the first 2 weeks following trauma. Further research is necessary to clarify the relationship between chronic symptoms after MTBI and MRI abnormalities. It may, thus, be possible to provide optimal strategies for emergency department management, to define a group of patients with a need for acute and rehabilitative intervention after MTBI, and to predict their outcome.