The endoscope has revolutionised the diagnosis and treatment of diseases of the nose and paranasal sinuses. It has enabled us to detect and diagnose many conditions that would hitherto go unnoticed and therefore untreated with speculum examination. Whilst operating, we have the advantage of good illumination and clear vision with minimally invasive surgery. Functional endoscopic sinus surgery (FESS) aims at maintaining physiological function and anatomical structure. The extent of the operation is adapted according to each case. It is focused on the ostiomeatal complex in the middle meatus and the ethmoid cells. The term FESS is used to draw attention to the potential for re-establishing sinus drainage and mucosal recovery. With FESS, it is possible to achieve consistently good results, provided the surgery is done accurately and with care. Most of the reported complications are minor. Major complications require an immediate aggressive medico-surgical treatment to minimise the sequelae. Chronic sinusitis not responding to medical treatment and nasal polyposis are two classical indications for performing endoscopic sinus surgery.