For unknown reasons, the morbidity and mortality from asthma are increasing in many parts of the world, making it a global health concern. The heterogeneous nature of the clinical manifestations and therapeutic responses of asthma in both adult and pediatric patients indicate that it may be more of a syndrome rather than a specific disease entity. Numerous factors, including viral infections, allergen and irritant exposure, and exercise, among others, complicate both the short- and long-term management of asthma. Therapeutic intervention has focused on the appreciation that airway obstruction in asthma consists of bronchial smooth muscle spasm and variable degrees of airway inflammation characterized by edema, mucous secretion, and the influx of a variety of inflammatory cells. Choosing appropriate medications depends on the disease severity (intermittent, mild persistent, moderate persistent, severe persistent), patterns of disease activity (exacerbations related to viruses, allergens, exercise, etc), and the age at onset (infancy, childhood, adulthood).