Object. The Glasgow Outcome Scale (GOS) is widely used to assess outcome after head injury, but is recognized as having a number of shortcomings that are highlighted and investigated in this study. The authors pursued two goals: 1) investigating the practicality of using a standard set of questions as part of a structured interview to assign GOS scores, and 2) studying the role of preinjury problems in confounding postinjury assessment of disability. Methods. Several of the major limitations of the GOS appear to arise from the use of a format that encourages impressionistic ratings. In the present study the authors examined the use of a standard interview for assessing the GOS covering five areas of social disability. Ratings were made for 80 head-injured patients. The results show that the rating based on the GOS provides an assessment of disability that is more complete than that given by an alternative scale of functional disability (Disability Rating Scale [DRS]) and much more complete than an assessment of physical disability (Barthel Activities of Daily Living [ADL] index). A measure of preinjury dependency was made revealing that, within this sample, 20% of patients required supervision in basic ADL before their injury. Conclusions. Assignment of GOS scores based on information obtained using a structured interview format provides a more comprehensive assessment of disability than using the DRS or the ADL index. There is a need to standardize attitudes about preinjury dependency in assessing disability after head injury.