The authors described 21 patients aged 37 to 83 with ossification of the posterior longitudinal ligament (10 with ischemic myelopathy, 6 with aftermaths of a trauma of the cervical spine, and 5 with the radicular syndrome on the basis of vertebral osteochondrosis. X-ray signs of three types of ossification of the posterior longitudinal ligament were defined and specified: linear, curved and mixed. The linear type was more frequently observed in the cervical spine whereas the curved type was more frequent in the lumbar spine.