It is a Minimally invasive sinus surgery under guidance of various degrees of nasal endoscopes without skin incision.with this procedure ventilation and drainage of sinuses is established preserving the nasal and sinus mucosa and its function of Mucociliary clearance.precise removal of tissues with sharp cuts with help of fine instruments and microdebrider without stripping the mucosa is possible.it is treatment of choice for patients with chronic bilateral sinusitis, polyposis, fungal sinusitis etc.