Since asthma has been recognized as a chronic inflammatory airway disease, inflammatory markers are useful tools to show the degree of allergic airway inflammation. Asthmatic airway is characterized with infiltration of activated Th2 lymphocyte, eosinophils and mast cells/basophils. Eosinophil derived proteins such as ECP, MBP and EDN are important markers indicating eosinophilic inflammation. Histamine and tryptase are the products of mast cell/basophil activation. These markers are detected in sputum, BALF, serum and urine, and increased in asthmatics. In addition to these markers, NO concentration in exhaled air, cytokines such as IL-4, IL-5, chemokines such as RANTES, eotaxin, LTE4, MMP are inflammatory markers to indicate the quality and quantity of asthmatic airway inflammation. Assessment of these markers, therefore, contributes to better control of asthmatic symptoms with appropriate therapy.