Routine cerebral CT scanning of patients with minor head injuries has been advocated as a screening procedure for hospital admission. The purpose of this study was to determine whether there were characteristics of the trauma patient with a minor head injury. Glasgow Coma Scale (GCS) of 13-15, that would predict a positive cerebral CT scan. An analysis of 200 patients with potential head injuries transported to our regional trauma center was performed. The following characteristics were analyzed as possible predictors: scene GCS (SC-GCS), emergency room GCS (ER-GCS), a change in GCS from scene to emergency room, loss of consciousness (LOC), and focal neurological deficit. Forty-eight per cent (96/200) of the patients underwent CT scanning of the head. CT scans were positive in 4 per cent (8/200) of the total group and 8.3 per cent (8/96) of those who underwent CT scanning. In the patients without LOC and ER-GCS of 13-15, all CT scans were negative (95% confidence interval 0.0% to 3.4%). In the 93 patients with LOC, eight patients had a positive scan (P < 0.001). Of the nine patients who sustained a skull fracture, five had a positive CT (55.6%; 95% confidence interval 21.2% to 86.3%) (P < 0.0001). Of all the patients with positive CT scans, two underwent emergent craniotomy: one for a depressed skull fracture with underlying contusion, the other for a temporal bone fracture and an epidural hematoma. Both patients had LOC and SC-GCS and ER-GCS of 15.(ABSTRACT TRUNCATED AT 250 WORDS)