56 patients suspected of having suffered recurrent disc prolapse in the lumbar region were examined by CT and by myelography; the value of these examinations has been analysed. In 32 patients the findings were checked during surgery. There were difficulties in diagnosis, both for CT and myelography, where the findings were complex, i.e. in patients in whom there was postoperative fibrosis as well as disc prolapse and/or osseous spinal canal stenosis. As regards recurrence of prolapse, sensitivity for both methods was 83%. Postoperative scar formation can be clearly demonstrated by CT, but myelography produced a false positive diagnosis of recurrent prolapse in 17%. The changes were, in fact, caused by scar tissue formation.