Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) often develop into emergency situations that are associated with high morbidity and mortality. There is still a lack of a generally accepted definition for the risk stratification in AECOPD to guide an optimal diagnosis and treatment. In this article we propose a classification based on 4 degrees of severity, depending on whether outpatient treatment can be done by the patient himself or is provided by a physician and whether inpatient treatment is carried out on a general ward or on an intensive care unit. The pharmacological therapy of AECOPD relies on short acting bronchodilators, systemic corticosteroids and in case of purulent sputum on antibiotics. Longacting beta(2)-agonists or anticholinergics, theophyllin, mucolytic drugs or mechanical percussion to the chest by a physiotherapist have no proven value in the emergency treatment of AECOPD. In respiratory failure the use of oxygen therapy and non-invasive positive pressure ventilation (NIPPV) can often prevent the need for endotracheal intubation and controlled mechanical ventilation, thus preventing associated risks like the development of nosocomial pneumonia.