Purpose: $S100{\beta}$, a marker of traumatic brain injury (TBI), has been increasingly focused upon during recent years. $S100{\beta}$, is easily measured not only in cerebrospinal fluid (CSF) but also in serum. After TBI, serum S 10019, has been found to be increased at an early stage. The purpose of this study was to evaluate the clinical correlations between serum $S100{\beta}$, and neurologic outcome, and severity in traumatic brain injury. Methods: From August 2006 to October 2006, we made a protocol and studied prospectively 42 patients who visited the emergency room with TBI. Venous blood samples for $S100{\beta}$, protein were taken within six hours after TBI and vital signs, as well as the Glasgow Coma Scale (GCS), were recorded. The final diagnosis and the severity were evaluated using the Abbreviated Injury Score (AIS), and the prognosis of the patients was evaluated using the Glasgow Outcome Score (GOS). Results: Thirty-eight patients showed a favorable prognosis (discharge, recovery, transfer), and four showed an unfavorable prognosis. Serum $S100{\beta}$, was higher in patients with an unfavorable prognosis than in patients with a favorable prognosis, and a significant difference existed between the two groups ($0.74{\pm}1.50\;{\mu}g/L$ vs $7.62{\pm}6.53\;{\mu}g/L$ P=0.002). A negative correlation existed between serum $S100{\beta}$, and the Revised Traumatic Score (R2=-0.34, P=0.03), and a positive correlation existed between serum $S100{\beta}$, and the Injury Severity Score (R2=0.33, P=0.03). Furthermore, the correlation between serum $S100{\beta}$, and the initial GCS and the GCS 24 hours after admission to the ER were negative (R2=-0.62, P<0.001; R2=-0.47, P=0.005). Regarding the GOS, the mean serum concentration of $S100{\beta}$, was $7.62\;{\ss}{\partial}/L$ (SD=${\pm}6.53$) in the expired patients, $1.15\;{\mu}g/L$ in the mildly disable patient, and $0.727\;{\mu}g/L$ (SD=${\pm}0.73$) in the recovered patients. These differences are statistically significant (p<0.001). Conclusion: In traumatic brain injury, a higher level of serum concentration of $S100{\beta}$, has a poor prognosis for neurologic outcome.