The Dutch guideline 'Diagnostics and treatment of severe asthma' provides recommendations on the diagnosis and treatment of patients older than 18 years with severe asthma. A checklist was developed to determine which diagnostic trajectory should be implemented in patients with 'difficult to treat asthma' before the diagnosis of 'severe asthma' can be made. Evidence-based recommendations are made in accordance with the GRADE method, with regard to additional treatment on top of the standard treatment of high dosages of inhaled corticosteroids combined with long-acting beta2 agonists. Furthermore, recommendations are made on the monitoring and follow-up of patients with severe asthma and on the setting up of specialized centres for patients suffering from severe asthma. This guideline is primarily meant for pulmonologists. However, it may also be useful for other disciplines involved in the care for patients with asthma.