A retrospective study was conducted on 21 consecutive patients with combined clinical and radiologic evidence of posttraumatic syringomyelia. Medical records and radiologic studies were reviewed to determine the following: age at injury, mechanism of trauma, spinal column injury and resultant neurologic deficit, latency period between injury and clinical manifestations of posttraumatic syringomyelia, clinicoradiologic findings of posttraumatic syringomyelia, and results of treatment. The patients were found uniformly to have sustained significant trauma (gunshot wounds, falls, or vehicular accidents) with marked neurologic dysfunction at the time of injury. Latent periods ranged from 1 month to 23 years. The most commonly presenting symptoms were radicular pain, spasticity, sensory loss, hyperhidrosis, and weakness. The most common physical findings were spasticity, hypesthesia, and weakness. Long term followup was obtained in 17 (81%) of the cases and suggested a higher rate of satisfaction among patients treated with surgical decompression of the syrinx. Radicular pain and sensory disturbance responded most predictably to surgical intervention, whereas spasticity responded least favorably. It is concluded that posttraumatic syringomyelia is a potentially disabling but treatable late complication of spinal injury, warranting a high index of suspicion among physicians who observe patients with such trauma.