Asthma is a chronic inflammatory airway disorder associated with airflow obstruction and bronchial hyper-responsiveness, which affects about 10% of population in Hong Kong. It is a major respiratory disease in Hong Kong that carries significant morbidity and high hospitalization burden in all ages. The use of long-term inhaled corticosteroid (ICS) treatment in recent decades has become the cornerstone in the treatment of most patients with persistent asthma with reduction in its mortality and hospital utilization. The ultimate goal of treatment is to achieve optimal control of airway inflammation and to reduce mortality and morbidity.