Advances in endoscopic sinus surgery have led to development of applications never imagined before for treating both adult and pediatric patients with sinus disease. Since 1925, when Maltz introduced for the first time a telescope in the nose, an incredible diag nostic tool was born; Since then, European and American visionares such as Kennedy, adopted the technique and perfectioned it to our days, when the application of the "new millenium" technologies, have made endoscopic endonasal procedures a fascinating chapter of nasal surgery. Attention to the details of this complex treatment strategy is needed to reap the full benefits of it, to avoid complications and to recognize unsolved problems in order to make every treatment the ideal one. As an ENT surgeon, you must keep in mind that the single most important contraindication for endonasal surgery, is not some kind of nasal condition but the inability of a surgeon to understand the intrincated and complex anat omy and physiology, knowledge of them both are the most valuable tools when perform ing a surgery, making it safe and helpful to the patient.