The purpose of this study is to assess the differences of the lumbosacral angles between the lying and standing position among Iumbago patients. Among Iumbago patients the following diseases with known causes were exclused in this study; spondylolisthesis, spondylolysis, pure herniated nucleus pulposus, tuberculous spondylitis, congenltal anomalies, trauma and psychosis etc. Only the following with unknown causes were included; idlopatic lumbago, hernlated nucleus pulposus with bone and joint changes, instability and degenerative osteoarthritis. The following lumbosacral angles were measured and evaluated in 460 lumbago patients; 271 patients in the lying position and 189 patients in the standing position. 1. Ferguson angle 2. Sacrovertebral angle (Mitchell angle) 3. LS horlzontal angle 4. Promonotorium angle 5. Line of weight bearing The results were summarized as follows; 1. Ferguson angle Lying position 38.4 Standing positon 35.3 Sacrovertebral angle 140.7 142 L5 horizontal angle 20.4 17.4 Promontorlum angle 134.4 134.9 2. Ferguson and L5 horizontal angles in lumbago patients were increased in the lying position and decreased in the standing position as compared with the angles in normal individuals (control group). 3. Sacrovertebral angle In lumbago patients was decreased in the lying position. 4. Promonotorium angle in lumbago patients was increased in the lying and standing position. 5. Judging by the Iine of weight bearing, Iumbago patients in the:lying position showed more instability as compared with that in the standing position group.