Posttraumatic syringomyelia is becoming increasingly recognized as a sequel to major and minor spinal cord injury, paralleling the development and widespread availability of magnetic resonance imaging as a diagnostic modality for evaluating possible spinal pathologic lesions. Delayed, subacute, or progressive neurologic deterioration in victims of traumatic spinal injury with "fixed deficits" should raise the suspicion of posttraumatic syringomyelia. Alternatively, it may present as sensory or motor complaints occurring on a delayed basis after minor spinal trauma causing no initial neurologic impairment. At our institution, we have treated six of eight patients with this condition by shunting fluid from the intramedullary cyst to the peritoneal cavity by means of a simple valveless shunt, resulting in sustained neurologic improvement in five patients.