The humanized monoclonal anti-IgE antibody omalizumab is currently the only biologic drug approved for asthma treatment. Omalizumab inhibits allergic responses by binding to serum immunoglobulins E (IgE), thus preventing their interactions with cellular IgE receptors. Omalizumab is also capable of down-regulating the expression of high affinity IgE receptors on inflammatory cells, as well as the numbers of eosinophils in both peripheral blood and induced sputum. The clinical effects of omalizumab include relevant improvements in respiratory symptoms and quality of life, paralleled by a marked reduction of asthma exacerbations, emergency room visits, and use of systemic corticosteroids and rescue bronchodilators. Moreover, some recent studies suggest potential benefits of omalizumab also in non allergic phenotypes of severe asthma. Very interesting are also further recent reports referring to the potential inhibitory effect of omalizumab with regard to bronchial structural changes, especially occurring in severe asthma and globally defined as airway remodeling. Omalizumab is relatively well tolerated, and only very rarely induces anaphylactic reactions. Therefore, this drug represents a valid option as add-on therapy for patients with severe persistent asthma, inadequately controlled by high doses of standard inhaled treatments.