Study objective: A decision instrument based on 5 clinical criteria has been shown to be highly sensitive in selecting patients who require cervical spine imaging after blunt trauma, while simultaneously reducing overall imaging. We examine the performance of this instrument in the elderly and explore some of the common features of geriatric cervical spine injury (CSI). Methods: The National Emergency X-radiography Utilization Study (NEXUS) was a prospective, observational, multicenter study conducted at 21 geographically diverse centers. We analyzed the performance of the NEXUS decision instrument among patients at least 65 years of age. Results: The study group consisted of 2,943 (8.6%) geriatric patients, representing 8.6% of the entire NEXUS sample. The rate of CSI was twice as great in these patients as it was in nongeriatric patients (4.59% versus 2.19%). Odontoid fractures were particularly common in geriatric patients, accounting for 20% of geriatric fractures compared with 5% of nongeriatric fractures. The frequency of patients meeting NEXUS criteria was similar in the 2 groups, with 14% of geriatric patients and 12.5% of nongeriatric patient classified as low risk. CSI occurred in only 2 low-risk geriatric patients, and these patients' injuries met our preset definition of a clinically insignificant injury. The sensitivity of the NEXUS decision instrument for clinically significant injury in the geriatric group was therefore 100% (95% confidence interval 97.1% to 100%). Conclusion: The prevalence of CSI, and especially odontoid fracture, is relatively increased among geriatric patients with blunt trauma. The NEXUS decision instrument can be applied safely to these patients, with an expected reduction in cervical imaging comparable with that achieved in nongeriatric patients. [Ann Emerg Med. 2002;40:287-293.]