The need for reintubation within 24-72 h of planned extubation is a common event, occurring in 2-25% of extubated patients. Risk factors for extubation failure include being a medical, multidisciplinary or paediatric patient; age >70 years; a longer duration of mechanical ventilation; use of continuous intravenous sedation; and anaemia (haemoglobin <10 g/dl or haematocrit <30%) at the time of extubation. The pathophysiology of extubation failure can be distinct from that seen with weaning failure and includes upper airway obstruction, inadequate cough, excess respiratory secretions, encephalopathy, and cardiac dysfunction. Extubation failure prolongs the duration of mechanical ventilation, increases the length of ICU and hospital stay, increases the need for tracheostomy, and is associated with a higher hospital mortality. Great emphasis has been placed on accurately predicting extubation outcome because extubation delay is also associated with increased length of stay and mortality. Tests designed to assess for upper airway obstruction, secretion volume, and the effectiveness of cough seem most promising for improving the decision to extubate. Mortality increases with delays in reintubation for patients failing extubation. Timely identification of patients at elevated risk of extubation failure followed by rapid re-establishment of ventilatory support can improve outcome.