Abstract Non-invasive positive pressure ventilation (NIV) is the provision of mechanical positive airway pressure ventilatory support through the patient’s upper airway through mask interface. Conditions in which it has been shown to be effective are acute cardiogenic pulmonary oedema and acute hypercapnic exacerbations of chronic obstructive pulmonary disease. In such conditions, NIV is associated with reduced intensive care unit demands, a reduction in intubation rates, reduced health-care expenditure and improved survival. Other conditions, such as hypercapnia of other cause, hypoxaemic respiratory failure and acute asthma, have supportive, but less conclusive data. Indications, contraindications and guidelines for the use of NIV are discussed.