Patients (16) with posttraumatic spinal cord cysts (PTSCC) were evaluated clinically and studied with metrizamide computed tomography (MCT). These patients presented months to years following a severe spinal cord injury, usually with new or progressively worsening neurological symptoms. The development of the PTSCC was unrelated to the location, type and severity of injury or to the time interval from the original injury. MCT showed that these cysts occur most frequently in normal or atrophic cords, they may be multiple, they most frequently are found in the dorsal portion of the cord, and they may vary along their length in width and position within the cord. Knowledge of this radiographic morphology is crucial to surgical planning. The location of the cysts and the mode of their enlargement are correlated with anatomic features of the spinal cord and changes in CSF dynamics. Cyst-to-subarachnoid space shunting relieves the majority of symptoms.