Functional Endoscopic Sinus Surgery (FESS) is a surgical modality for some diseases of the nose and paranasal sinuses. FESS is a minimally invasive technique in which sinus air cells and sinus ostia are opened under direct visualization. The goal of this procedure is to restore sinus ventilation and normal function. It is a relatively recent surgical procedure that uses the help of nasal endoscopes. FESS (like any sinus surgery) is most successful in patients who have recurrent acute or chronic infective sinusitis. Patients in whom the predominant symptoms are facial pain and nasal blockage usually respond well. The sense of smell often improves after this type of surgery. The main advantage of FESS compared with traditional techniques is that it is less invasive, resulting in minimal postoperative discomfort. Scars and damage to the nerve supply of the teeth are also avoided. The use of the endoscope permits a better view of the surgical field, and this is probably responsible for the lower rate of complications. Postoperatively, it is important to keep the nose as free from build-up of crusts as possible. Normal function usually returns within one to two months. Complications are minimal and depends on the expertise of the surgeon. The few are 1) blindness resulting from damage to the optic nerve. 2) Cerebrospinal fluid leak is the single most common major complication of FESS, occurring in about 0.2 percent of cases. 3) Orbital hematoma and nasolacrimal duct stenosis.