This prospective study was set up to record the changes in the intervertebral disc accompanying resolution of sciatica following conservative treatment. Patients presenting with sciatica (n = 165) were examined by computed tomography (CT) of the lumbar spine. Disc lesions were classified into the following groups: herniation, sequestration, generalized bulge and focal bulge. Follow-up CT of the pathological disc was performed in 106 of the 165 patients after 1 year and identical anatomical sections were compared. All patients were initially treated conservatively by the injection of steroid and local anaesthetic at the intervertebral disc/nerve root interface. Of 84 cases of disc herniation and sequestration 64 (76%) showed either complete or partial resolution on follow-up CT examination. Of 22 cases with either a generalized or focal bulge of the disc 18 (82%) were unchanged on follow up. The classical disc herniation in a young patient is the type of disc lesion most likely to show greatest improvement at follow-up CT.