BACKGROUND: Assessment of the cervical spine (c-spine) in the obtunded blunt trauma patient remains a diagnostic dilemma. In 2002, our institution implemented a new c-spine clearance guideline utilizing c-spine computed tomography (CT) and magnetic resonance imaging (MRI). This study evaluates the safety and efficacy of this guideline. METHODS: Obtunded blunt trauma patients admitted over a 1-year period, who underwent both a c-spine CT and a c-spine MRI, were identified. Records were reviewed for demographics, mechanism, diagnostic evaluations, injuries, and outcome. RESULTS: Fifty-two patients met inclusion criteria. On average, patients underwent a c-spine CT on postinjury day 0.4 and MRI on postinjury day 4. Forty-four patients had a negative c-spine CT, of whom 13 (30%) had a positive MRI for ligamentous injury (p < 0.01). Thirty-one patients had both a negative CT and a negative MRI. All patients (n = 8) with positive CTs had positive MRIs. The average Injury Severity Score, Abbreviated Injury Score head and neck, length of stay, and outcome was not significantly different for patients with a c-spine injury. No missed c-spine injuries and no areas of cervical collar-related skin breakdown were seen in follow up. CONCLUSIONS: In the obtunded patient, expeditious c-spine evaluation is important. Both missed injuries and prolonged unnecessary immobilization can result in adverse outcomes. This study confirms that c-spine CT, when used in combination with MRI, provides a safe and efficient method for c-spine clearance in this patient population. CT alone misses a statistically significant number of c-spine injuries.