Symptom prevalence of OPLL is estimated between 20% and 50%. Patients with OPLL have neurological disorders, pain/numbness, and trunk stiffness. These symptoms of stenotic myelopathy and of ossification. spondylosis deteriorate patients'quality of life. The ossification extends and elongates very gradually and tiny ossification at first visit hardly grows up to enough to cause myelopathy. A majority of patients experience a chronic course, but some suffer spinal cord injury. Preemptive surgery should be carefully contemplated because definite criteria have not been established yet.