The treatment of chronic sinusitis has four objectives: to control infection, to reduce tissue edema, to facilitate the drainage of sinus secretions and to maintain ostial permeability. Medical treatment includes antibiotics, decongestants, mucolytics, steroids and analgesics. Surgical treatment may be conservative, functional or radical. At present, "FESS" is the "Golden Standard". It is focused on the middle ostiomeatal complex and the ethmoid cells. The extent of the operation is adapted according to each case. In spite of standardization of the operative procedure, this type of surgery is risky. Most of the reported complications are minor. Major complications require an immediate aggressive medico-surgical treatment to minimize the sequelae. Precise and complete pre-operative evaluation, good preparation of the patient, meticulous and adapted surgical technique and experience acquired through a regular practice of this type of surgery play a major role to lower the risks of complications.