The term bronchiolitis refers to inflammatory disorders of the bronchioles. Constrictive bronchiolitis is the type most frequently encountered.The term bronchiolitis refers to inflammatory disorders of the bronchioles. Constrictive bronchiolitis is the type most frequently encountered.The main clinical manifestations include the development of exertional dyspnoea and fixed airflow obstruction. Chest x-ray findings are usually unhelpful, but CT scanning may reveal a mosaic pattern on expiration. Peripheral micronodules are less frequently seen. The causes of constrictive bronchiolitis are numerous. The diagnosis may be clear from the clinical context when a causative event or predisposing condition can be identified (lung or bone marrow transplantation, toxic fume or gas inhalation, rheumatoid arthritis); in other conditions, a stepwise approach to the diagnosis is usually recommended in order to exclude other causes of subacute or chronic obstructive disease. Formal diagnosis requires histological examination of surgical lung biopsies. Despite corticosteroid administration, respiratory failure usually develops. Specific inhibitors of pro-inflammatory cytokines may offer a new and promising therapeutic approach.The term bronchiolitis refers to inflammatory disorders of the bronchioles. Constrictive bronchiolitis is the type most frequently encountered.The main clinical manifestations include the development of exertional dyspnoea and fixed airflow obstruction. Chest x-ray findings are usually unhelpful, but CT scanning may reveal a mosaic pattern on expiration. Peripheral micronodules are less frequently seen. The causes of constrictive bronchiolitis are numerous. The diagnosis may be clear from the clinical context when a causative event or predisposing condition can be identified (lung or bone marrow transplantation, toxic fume or gas inhalation, rheumatoid arthritis); in other conditions, a stepwise approach to the diagnosis is usually recommended in order to exclude other causes of subacute or chronic obstructive disease. Formal diagnosis requires histological examination of surgical lung biopsies. Despite corticosteroid administration, respiratory failure usually develops. Specific inhibitors of pro-inflammatory cytokines may offer a new and promising therapeutic approach.If the clinical context or the radiology and clinical findings are not highly suggestive of a constrictive bronchiolitis, a surgical lung biopsy should be considered.