The failed back surgery syndrome (FBSS) is a severe, long-lasting, disabling and relatively frequent (5-10%) complication of lumbosacral spine surgery. Wrong level of surgery, inadequate surgical techniques, vertebral instability, recurrent disc herniation, and lumbo-sacral fibrosis are the most frequent causes of FBSS. The results after repeated surgery on recurrent disc herniations are comparable to those after the first intervention, whereas repeated surgery for fibrosis gives only 30-35% success rate, and 15-20% of the patients report worsening of the symptoms. Computerized tomography (CT) with contrast medium and, in particular, Gd-DPTA enhanced MRI have recently allowed a differentiation between these two pathologies permitting us to adopt different therapies. In 1982-92 we applied spinal cord stimulation (SCS) as a first therapy of FBSS with proven lumbo-sacral fibrosis. Fifty-five patients underwent percutaneous trial SCS with a mono/multipolar electrode placed at the level of Th9-12. In the 36 patients who had a positive response to the trial stimulation, the electrode was connected to an implantable neurostimulator. On January '94 a third party, not involved in the treatment of the patients, controlled 34 of the 36 patients with a mean follow-up of 55 months. We classified the patients reporting at least 50% pain relief and satisfaction with result as successful, and 56% of the patients fell in that category. 10 out of 34 patients were able to resume their work. The success rate was significantly higher in females (73%) than in males, and in radicular rather than axial pain. Our data have led us to consider SCS as a first choice treatment in FBSS due to lumbo-sacral fibrosis.