Asthma is a chronic disease characterized by reversible airway obstruction, airway hyper- responsiveness, and inflammation of airways. Th2 cells, one sort of CD4+ T lymphocytes, are currently considered to play an important role in the chronic airway inflammation of asthma. Meanwhile, a number of laboratories have clearly established the importance of the Th2-derived cytokine interleukin-4 (IL-4) in mediating the airway inflammatory response. Anti-IL-4 therapy might be beneficial in treatment of chronic asthma.