The objective of this study was to develop one instrument for assessing quantitatively the disability of severe head trauma patients so their rehabilitative progress could be followed from coma through different levels of awareness and functioning to their return to the community. This disability rating (DR) instrument was designed to be easily learned, quickly completed, valid, predictive of outcome and to have a high inter-rater reliability. The DR Scale consists of 8 items divided into 4 categories; 1. Arousal and awareness; 2. Cognitive ability to handle self-care functions; 3. Physical dependence upon others; 4. Psychosocial adaptability for work, housework, or school. Completed independently by several raters for more than 88 serious head injury patients, inter-rater correlations were highly significant. The admission DR was significantly related to clinical outcome at 1 year after injury and was significantly related to electrophysiologic measures of brain dysfunction as reflected in degree of abnormality of evoked brain potential patterns. The DR Scale is more sensitive than the Glasgow Outcome Scale in detecting and measuring clinical changes in individuals who have sustained severe head trauma. Also it can be used to help identify patients most likely to benefit from intensive rehabilitation care within a hospital setting. It provides a shorthand global description of a head injury patient's condition that facilitates understanding and communication.