Asthma accompanied by chronic airways obstruction (CAO) is frequent and raises difficult clinical problems. Persistent inflammation of the airways is the main factor responsible for obstruction. There are no symptoms that distinguish this form of asthma from non-asthmatic chronic obstructive lung disease, and only respiratory function tests can confirm the diagnosis of CAO. Pharmacological tests with bronchodilators evaluate the bronchomotor part of CAO which is substantial in asthma as opposed to other causes of obstructive lung diseases. A negative test cannot exclude the diagnosis and suggests that the obstructive component due to bronchial inflammation is predominant. In such case a reversibility test performed with corticosteroids is of considerable interest as it reduces the partly reversible inflammatory part of the obstruction. Peak flow curves provide more precise date on the evolutive type of CAO and therefore contribute to a great extent to the monitoring and education of patients. Severe chronic asthma with high annual systemic corticosteroid consumption requires special care and justifies the current attempts made to replace corticosteroids by other anti-inflammatory drugs.