Objective : The tethered cord syndrome results in progressive neurological deficits. Although it may remain controversial, many physicians recommend definitive surgery to untether the cord as soon as this condition is identified. We retrospectively evaluate the pre-operative and post-operative course of 38 tethered cord patients with spinal dysraphism in an attempt to learn the natural history of the disease and to determine the effectiveness of the surgical treatment. Methods : The medical records, operation notes and radiographs were evaluated. The follow up period ranged from 4 months to 12 years with a mean follow-up of 28.6 months. Twenty-seven patients were younger than 15 years of age. Results : At presentation, 26 of the patients were asymptomatic. In three of 11 adult symptomatic patients, their neurological deficits worsened after trauma or exercise. Improvement of motor strength was documented in two out of 5 patients. Five of nine patients with bladder symptoms improved, however, none had a complete return of their bladder function. Conclusion : Childhood patients were less symptomatic than the adult patients. Adult patients showed progression of their symptoms that were not improved even after the operation in most of the cases. Asymptomatic tethered spinal cord can be symptomatic as time passes by and even at an old age. Future research should be focused on the operative methods to prevent the delayed deterioration after surgery, rather than on the usefulness of preventive surgery in asymptomatic patients.