OBJECTIVE Debilitating neurobehavioural sequalae often complicate traumatic brain injury (TBI). Cognitive deficits, particularly of attention, memory, information-processing speed and problems in self-perception, are very common following severe TBI. METHODS The Neurobehavioural Rating Scale (NRS) is a multi-dimensional clinical-based assessment instrument designed and validated to measure neurobehavioural disturbances following TBI. This study examined 41 patients who were admitted to the intensive care unit of the Department of General Neurosurgery at Cologne University Hospital after severe TBI between January 1995 and July 2003. All 27 items of the NRS were assessed 6 and 12 months post-injury. RESULTS Subjects after severe TBI (GCS<9) showed relatively high overall scores on the NRS, reflecting a high degree of overall neurobehavioural dysfunction. NRS items did not change significantly between 6 and 12 months post-trauma for anxiety, expressive deficit, emotional withdrawal, depressive mood, hostility, suspiciousness, fatigability, hallucinatory behaviour, motor retardation, unusual thought content, liability of mood and comprehension deficit. There was a tendency of improvement for inattention, somatic concern, disorientation, guilt feelings, excitement, poor planning and articulation deficits. For conceptual disorganization, disinhibition, memory deficit, agitation, inaccurate self-appraisal, decreased initiative, blunted affect and tension even a tendency for further deterioration in the post-traumatic follow-up was detected. Changes between 6 and 12 months post-TBI were statistically significant for disorientation (improvement), inattention/reduced alertness (improvement) and excitement (deterioration). CONCLUSIONS The data shows that neurobehavioural deficits after TBI do not show a general tendency to disappear over time. Some aspects related to self-appraisal, conceptual disorganization and affect may even deteriorate, thereby presenting a challenging problem for both the patients and relatives. This is in contrast to the parallel improvement of post-traumatic sensomotoric deficits.