Elevation in osmolality occurs after both injury and experimental hemorrhage. Similar elevations in glucose and cortisol have been found to correlate with both injury severity and survival. In this study, we have investigated the relationship between the severity of trauma and changes in glucose, osmolality, and cortisol in injured patients. Trauma severity was estimated using the Injury Severity Score, and correlation coefficients were computed for the three measured variables. Elevations in both osmolality and glucose correlated positively with severity of injury, whereas cortisol did not correlate. Although glucose and alcohol contributed to the rise in osmolality, they did not account for the entire increase.The results indicate that measured increases in osmolality and glucose following trauma may be useful in the prospective evaluation of its severity, especially in those patients with occult major injury. The lack of correlation of increased cortisol with injury severity suggests an interaction of multiple hormones resulting in the increase in osmolality and glucose.