There is no uniformly accepted protocol for the radiological assessment of the cervical spine in critically ill trauma patients. The Alfred Trauma Centre receives about 40% of Victorian patients with major trauma. A protocol was developed for cervical spine evaluation, comprising three plain X-rays and a swimmer's view added when necessary to visualize C7-T1, CT and/or MRI for abnormal regions, and functional (flexion/extension) X-rays to exclude cervical spine instability due to soft tissue trauma. Functional X-rays were performed "actively" in conscious patients and "passively" in unconscious patients. One hundred consecutive patients were prospectively evaluated and 91 survived to complete data collection. Six (6.6%) had unstable cervical spine injuries--five detected with plain X-rays and one (1.1%) detected only with passive functional X-rays. Static cervical X-rays cost $93.00 per patient. Functional cervical X-rays added $42.00 per patient and were uncomplicated. Collar complications were common when collars remained on for more than 72 hours. This low detection rate is clinically important because of the enormous potential social and economic costs of missed unstable cervical spine fractures.