Intradural disk herniation is a rare condition. Most of reported cases involve the lumbar spine and have histories of chronic low back pain followed by an acute episode of radicular pain with neurologic deficit. The authors report the myelographic and lopamidol-CT findings in a case of a L4-5 intradural disk herniation. These two examinations demonstrated an intradural multilobular mass associated with an extradural component at the level of the disk space and with a same density as it. Anatomic adherences between dura-mater and posterior longitudinal ligament could explain the primary mechanism of these intradural disk herniations; but operative or traumatic antecedents are often noted. Most often operation discloses only the intradural component with a small anterior dural cleft, without extradural abnormalities. Postoperative follow up is usually good.