According to 1999 data from the Centers for Disease Control and Prevention, traumatic brain injuries (TBI) caused by motor vehicle accidents, firearms, and falls are recorded as a leading cause of death and lifelong disability for young adults in the United States. Researchers have investigated if correlations exist between variables in the acute stage of injury and outcome measures in TBI patients. The Glasgow Coma Scale (GCS) score is one variable that was extensively studied for its ability to predict outcome in TBI patients. However, the use of different designs and methodologies in these studies makes the interpretation of the cumulative findings difficult. Therefore the purpose of this review was to provide a summary of the research findings on the ability of the GCS scores to predict outcome in TBI patients. A search was done on MEDLINE (R) and CINAHL(R) to identify studies that investigated the predictive ability of the GCS score. Studies that used the GCS as a variable in predicting outcome with adult patients who had sustained some type of head injury were included. GCS scores are most accurate at predicting outcome in head-injured patients when they are combined with patient age and pupillary response and when broad outcome categories are used. The motor component of the GCS yields similar prediction rates as the summed GCS score, and better prediction occurs with very high or very low GCS scores. Information about the cumulative research findings on the predictive ability of GCS scores aids nurses in providing support and education to family members during the acute stage of injury, and in coordinating the services of members of the healthcare team, which could result in improved outcomes for both patient and family.