Failed back syndrome (FBS) refers to chronic backand/or leg pain that occur after back (spinal) surgery.About 30% of patients undergoing lumbosacral surgery“fail”. In this study we prospectivelyevaluated the clinicaloutcome of fifty six patients with FBS treated surgicallyin the Neurosurgical department of Cairo Universitybetween March 2009 and March 2010 to establish aproper algorithm for the surgical treatment of thesecases. All patients were operated upon by decompressionand/or fusion by a posterior approach. Satisfactoryoutcome was present in 46 patients (82%). Complicationsoccurred in 13 cases (23%). Length of the time intervalfor recurrence of symptoms especially sciatica after theinitial operation and the time interval of conservativetreatment correlated well with outcome. We concludedthat surgery for FBS can be very successful providedproper patient selection, good and thorough examinationand investigations and proper surgical technique.