Asthma affects 5.4 million people in the UK, around 1 in 12 of the population. Between 5 and 10% of asthma (depending on the definition used) is categorised as difficult asthma, a term which generally refers to patients who continue to experience symptoms and frequent exacerbations despite the prescription of high-dose asthma therapy. Difficult asthma is an indication for specialist review by an appropriate respiratory physician, but close liaison between primary, secondary and tertiary care is critical and it is therefore important that primary care health professionals should be aware of the principles of management. One of the most important questions to ask is whether the individual with difficult asthma is taking their treatment Identifying this, however, is not easy. GPs could assess prescription uptake, looking for low use of preventers and excess use of short-acting bronchodilators. Newer means of assessing adherence have been developed. Inhaler devices that can monitor completion and timing of actuations have been produced. Meters that measure FeNO are available. A recent UK study found that 12 out of 100 patients referred for difficult asthma did not have reversible airflow obstruction or a history suggestive of asthma. Diagnoses included COPD, cystic fibrosis, cardiomyopathy, respiratory muscle dysfunction and severe anxiety with vocal cord dysfunction.