With modern imaging techniques, various types of spinal dysraphism are being diagnosed in adults with increasing frequency. We report a 42-year-old woman with diastematomyelia whose symptoms characteristically were precipated by trauma. She exhibited other typical features such as a posterior midline hair patch and vetebral malformations. Metrizamide myelography with computerized tomography showed a bony septum at Tl 1 with a cleft at T9-T11 separating two dural tubes each of which contained a single spinal hemicord. The septum was excised with complete relief of symptoms.