Acute sinusitis frequently follows upper respiratory tract infections. Patients complain of headache, facial pain, fever and purulent rhinorrhoea. Diagnosis is based upon the symptoms, and treatment comprises symptomatic relief with analgesics, topical or systemic decongestants and steam inhalation. If indicated, antibiotics should be given for an adequate period of time. Patients with chronic sinusitis complain of a combination of nasal obstruction, rhinorrhoea and postnasal drip associated with intermittent facial pain, with symptoms persisting for 3 months or more. Predisposition to the condition may be caused by rhinitis (allergic or nonallergic) and anatomical variants. Failure of mucociliary transport and sinus ostial obstruction leads to mucosal oedema, mucous hypersecretion and chronic infection. Current treatment aims are to control rhinitis and improve ventilation and function of the sinuses. Rhinitis may be controlled with the long term use of topical corticosteroids, mast cell stabilisers or antihistamines, either alone or in combination. Secretions may be cleared with steam inhalation and/or saline nasal douching. Failure to control chronic sinusitis with medical treatment may indicate surgery. The aim of surgery is to improve ventilation and facilitate drainage of the sinuses, allowing the restoration of normal function. Removal of nasal polyps, reduction of inferior turbinates or septal straightening may be all that is required. Some patients will need endoscopic ethmoidectomy and middle meatal antrostomy. Improved ventilation in the ethmoid infundibulum may help to resolve disease in maxillary and frontal sinuses. Medical treatment of underlying rhinitis will need to be continued postoperatively, often in the long term, while special consideration needs to be paid to sinusitis in children, in relation to dental disease and in the immunosuppressed. Complications of acute and chronic sinusitis include intraorbital and intracranial sepsis. These potentially lethal complications need urgent evaluation with high resolution computerised tomography (CT) scanning, intravenous administration of broad spectrum antibiotics (including anaerobic and microaerophilic cover) and urgent surgical drainage as appropriate.