Most patients who have spondylolysis dont's need surgical treatment. However, for the patients who have no response to conservative treatment, surgical treatment may be indicated. In 1970, Buck reported the operative technique that the used two screws between the pars defect and lamina followed by bone graft. In patients who have spondyloysis, pain in the back seems to be due to instability and irritation of nerve root by the abnormal motion of the loose neural arch and granulation tissue. For period of 7 years from May, 1984 to March, 1991, twelve patients with spondyloysis who had no response to conservative treatment were treated with Buck's operation and were analyzed. Following results were obtained: 1. The age of the patients was 24 years in average ranging from 14 to 40 years. 2. The level of the lesion was L5 in 10 cases, L4 in 2 cases. 3. Preoperative clinical feature included low back pain in 12 cases, refered pain in 2 cases. 4. Clinical sympotoms were improved in 83%, and the follow up result of the operation: excellent 16.7%, good 66.6% and poor 16.7%.