Background: functional endoscopic sinus surgery (FESS) has revolutionized surgical care, opening new horizons in the management of chronic rhinosinusitis and other paranasal sinus disorders Messerklinger established and reinterated the importance of the sinus ventilation and pattern of mucociliary clearance. FESS was first described independently by both Messerklinger in German literature and Wigand. Aim of the work: this study aimed to assess the efficacy, safety and benefits of FESS in cases of chronic recurrent rhinosinusitis with or without nasal polyposis, fungal sinusitis,septal and turbinate pathology and CSF rhinorhea in terms of morbidity, mortality and recurrent of disease. Patients and Methods: This study was conducted in Bab Elshaerea University Hospital and Hearing and Speech Institute from July 2017 to August 2018. A total of 50 patients with clinical evidence of sinonasal diseases were categorized into 4 groups (Chronic recurrent rhinosinusitis with or without nasal polyposis (20 patients) ,fungal sinusitis (10 patients),septal and turbinate pathology(10 patients) and CSF rhinorhea(10 patients)). Patients were evaluated with nasal endoscopy and computed tomographic (CT) evaluation prior to FESS. Results: out of 50 patients, 26 were male and 24 were female in the present study. Male: female ratio was 52:48. Depending on symptoms, endoscopic examination and CT scanning, three patients only had a recurrence (Two patients from group of chronic recurrent rhinosinusitis with or without nasal polyposis and one patient from fungal sinusitis group). Conclusion: FESS provided an excellent and safe method for treating sinonasal disease. The success rates were encouraging, but because of the nature and chronicity of the disease, longer follow-up was necessary to truly assess the surgical effectiveness of the procedure.