All victims of major blunt trauma have been said to be at risk of cervical spinal injury. In a prospective study of 410 such patients at our institution, we identified 13 patients (6.12 per cent) with unstable cervical spines. Loss or defect of consciousness following injury (regardless of duration), neurological deficit consistent with cervical cord or nerve root injury and neck tenderness were significantly predictive of an unstable cervical spine. Immediate radiographic investigation of the cervical spine is mandatory in such patients, but may not be required in patients without these signs.