Two patients, men aged 42 and 40 years, developed new neurological symptoms 3 months and 22 years, respectively, after a traumatic high thoracic spinal cord injury. The MRI scan showed a cavity in the central part of the spinal cord, on which the diagnosis of 'posttraumatic syringomyelia' could be based. In one of the patients a syringo-subarachnoidal shunt was created, the other was treated conservatively because of a severe concomitant thoracic kyphosis. Posttraumatic syringomyelia is a potentially life-threathening late complication of spinal cord injury and is characterized by development of new neurological symptoms after a variable time interval. The most typical symptom of non-traumatic syringomyelia, viz. diminution of vital sensitivity without loss of gnostic sensitivity, is not necessarily present in posttraumatic syringomyelia. Surgical treatment of posttraumatic syringomyelia is advocated if there is progressive neurological deterioration, and consists of drainage of the syrinx.