BACKGROUND The timing of fracture fixation in patients with head trauma is controversial. Early fracture fixation may be associated with secondary brain injury. We undertook this study to investigate the effect of reamed intramedullary nailing on cerebral perfusion. METHODS Seventeen patients were identified who had placement of an intracranial pressure monitor and reamed rodding of the femur. Retrospective chart review was performed. RESULTS Average Injury Severity Score was 35 (range, 17-50). Cerebral perfusion pressure (CPP) decreased intraoperatively for all except one. The average decrease in CPP from pre- to intraoperative values was 17 mm Hg (p = 0.0012). Seventy percent had an average intraoperative CPP below 75 mm Hg, and all patients had a minimum CPP below 75 mm Hg. The decrease in CPP was mostly attributable to a corresponding decrease in mean arterial pressure. CONCLUSIONS Patients with head trauma undergoing femoral rodding need careful attention paid to managing blood pressure to minimize CPP decreases.