The follow-up of these seventy-three cases suggested the following conclusions:. 1. The clinical signs alone are not always sufficient to make the diagnosis of herniated nucleus pulposus with sufficient accuracy. 2. When positive, myelography was reliable as a means of localising the hernia. 3. In doubtful cases in which conservative treatment failed a clearly positive myelography turned the scale for a well-indicated operation. 4. In doubtful cases a clearly negative myelography has often rightly been a contra-indication for laminectomy. 5. No serious complication from the use of water-soluble contrast medium for myelography has been encountered