Indication of cranial computed tomography (CCT) for patients with head minor injury (MHI) is difficult. Actually, 90% of patients with MHI who have CCT under the present clinical decision rules have normal scans. Serum concentrations of the protein S-100B were recently found to provide useful information. We have investigated whether S-100B concentrations in patients with MHI can provide additional information to improve indication of the need for an initial CCT scan. One hundred five patients with MHI were enrolled in this prospective study, at the French university hospital of Marseille and Clermont-Ferrand. Of the 105 patients studied, 16 exhibited trauma-relevant intracerebral lesions on the CCT scan (CCT+). With a cut-off limit of 0,10 microg/L S-100B, CCT+ patients were identified with a sensitivity level of 100% and a specificity level of 33%. Adding the measurement of S-100B serum concentration to the clinical decision rules for a CCT scan in patients with MHI could allow a 30% reduction in scans.