This article reviews the use of non invasive ventilation (NIV) in the management of acute hypercapnic respiratory failure (AHRF). Most of the evidence and experience comes from treating acute exacerbations of chronic obstructive pulmonary disease (AECOPD) but this has been extrapolated to other conditions. Patient selection, contraindications, how to monitor and recognise when NIV is failing and what the options are then, are discussed. There are differences in criteria for initiation of NIV and the way that it is applied in patients with neuromuscular disease, chest wall disorders and obesity. The importance of staff experience and training as well as the need for regular audit are stressed.