This study was carried out to observe the efficiency of endoscopic sinus surgery in the management of middle meatus diseases. The study was done in our private clinics & in the ENT department of AL-yarmouk Teaching Hospital Baghdad - Iraq. This effort represent prospective study of 100 patient with sinonasal diseases who were underwent functional endoscopic sinus surgery. The main presenting symptoms of patient were nasal obstruction (76%), anterior nasal discharge (67%), headache (56%), facial pain (62%), hyposmia / anosmia (30%), post nasal drip (53%). Most of the patients have got partial or complete symptomatic relief. Minor complications of FESS occurred in (22%) which includes adhesions, minor epistaxis, infection and periorbital ecchymosis it was concluded that FESS is a safe & efficient method for dealing with different sinonasal diseases. Aims of the study: To evaluate the efficiency of functional endoscopic sinus surgery (FESS) in management of middle meatus diseases. Concept: The introduction of nasal endoscope has revolutionized the planning & treatment of nose & paranasal sinus diseases. In the 1960s Messerklinger began his work with endoscopic diagnosis and surgery of sinuses. The main indications for functional endoscopic sinus surgery are recurrent acute sinusitis that does not respond to medical therapy. Endoscopic nasal surgery have grown far beyond FESS & now include other nasal, orbital and anterior skull base procedures.