Asthma is a chronic inflammatory disorder of the airways in which many cells and cellular elements play roles. Interleukins 5 (IL-5) and 13 (IL-13) are cytokines which play important roles in the pathophysiology of asthma. Selective accumulation and activation of eosinophils in the bronchial mucosa is considered a central event in the pathogenesis of asthma. IL-5 acts as a mediator of activation of eosinophils, influencing adhesion, membrane receptor expression, chemotaxis, and mediator synthesis. Airway eosinophilia has been related to bronchial hyperreactivity, asthma symptoms, and airway narrowing in subjects with asthma. IL-13 has a great influence on bronchial hyperreactivity, inflammation, and airway remodeling. Moreover, this cytokine drives many cellular responses relevant in asthma, including epithelial cell maturation and mucus production, synthesis of extracellular matrix proteins, and enhanced contractility of airway smooth muscle cells. In recent years, efforts have been underway to use substances acting as antagonists of these cytokines in the treatment of asthma. Many studies are being performed to assess the efficacy of anti-IL-5 and anti-IL-13 antibodies as well as substances inactivating receptors of these cytokines in asthma therapy. The results of these studies seem very interesting and induced the authors to discuss this issue.