Functional endoscopic sinus surgery has a success rate for symptom improvement of over 90%. However, symptom improvement demonstrates poor correlation with disease resolution and approximately 20% of patients end up requiring revision surgery. Those patients requiring revision sinus surgery therefore fall into a minority but represent a therapeutic challenge for the otolaryngologist [6]. Prior to embarking on revision sinus surgery, a thorough reassessment of the patient’s underlying disorder should be conducted. A key concept to remember is that chronic sinusitis is a multifactorial disease with surgery serving as an adjunct to medical management and control of environmental factors. In addition, continued medical therapy will be necessary for the revision sinus surgery patient even following surgery [7]. In addition to complications arising from prior surgery, previous inadequate surgery, or poor postoperative management, other important issues leading to revision surgery can be classified as general host, environmental, and local host factors [5]. In those patients who have failed an initial attempt at endoscopic sinus surgery, a checklist should be completed evaluating each of these categories before revision surgery. (Table 20.1) The categories most amenable to revision sinus surgery are inadequate surgery or postoperative scarring either due to poor operative technique or inadequate postoperative care. Patients who underwent mucosal stripping from prior surgical intervention are at risk for the development of neo-osteogenesis, a problem that is very difficult or impossible to resolve with revision surgical intervention and appears to be associated with a poorer long-term prognosis and sometimes apparently with persistent pain.