Results of surgical treatment in 50 failed back surgery patients were retrospectively reviewed to determine what factors influenced surgical outcome. Before surgery, all patients had disabling pain and limited function. Overall significant improvement in pain and function was obtained in 66% of the patients. Thirteen of 16 patients (81%) who had successful fusion of pseudarthrosis had a satisfactory outcome, whereas only 3 of 13 patients (23%) who had failed pseudarthrosis repair had a satisfactory outcome. Successful pseudarthrosis repair is the key to a high clinical success rate in revision surgery for failed back surgery syndrome. Pseudarthrosis repair by conventional posterolateral fusion with postoperative lumbosacral corset immobilization showed a high failure rate. The success rate of reoperation on failed back surgery syndrome patients is low.