Our aim was to analyse causes for persistence of pain after lumbar discectomy and outcome of reoperations. Out of 37 reoperated patients, 22 with a minimum follow-up period of one year were included in this retrospective study concerning the years 1993 to 2000. All patients had previously undergone laminotomy and discectomy and fusion was not required during second operations. Outcome was evaluated according to the modified criteria of Kawabata et al. Overall incidence of reoperation was 6.5%. Reoperations were performed because of recurrent disc herniation in 9 patients, epidural fibrosis in 8, and de novo disc herniation at a different level in 5. Contrast enhanced computerized tomography was used in 17 patients and this might be the reason for misdiagnosis of recurrent disc herniation in the two patients with epidural fibrosis. In patients with de novo disc herniation, symptoms recurred earlier. In 20 patients, satisfactory relief of pain, as well as better outcome could be achieved (p<0.05), but no significant improvement in neurological deficits was observed. Excellent results were obtained more in patients with recurrent disc herniation and poor outcomes correlated with long (> 1 year) time intervals for onset of recurrent sciatica (p<0.05). However, patients with epidural fibrosis were also glad postoperatively for decreased pain severity. Only co-existence of epidural fibrosis and de novo disc herniation predicted an inferior outcome. Although recurrent disc herniation seemed to respond best to surgical treatment, we recommend reoperation when objective preoperative findings indicate the presence of surgically correctable compression regardless of its type.