A consecutive series of 45 cases of diastematomyelia in adults is analyzed. The majority of patients were females with a 3.4:1 female to male ratio. The ages ranged from 19 to 76 with a mean of 37.8 years. The lesion was usually located in the lumbar region. In 17 patients the development of symptoms was associated with specific incidents or events, usually trauma. Twelve patients had pre-existing static musculoskeletal or neurologic abnormalities and 20 had cutaneous spinal lesions suggesting dysphraphism. The symptoms and signs included pain and a variety of sensorimotor and/or sphincteric abnormalities. Metrizamide CT scanning proved to be the most useful diagnostic procedure. Only 4 patients were investigated by MRI and from the information available its role in the diagnosis of adult diastematomyelia is not established. Twenty-three of 24 patients treated by surgery showed marked improvement.