Peripheral blood eosinophilia and eosinophilic lung inflammation are common in a variety of pulmonary conditions, including eosinophilic pneumonia and asthma, hypereosinophilic syndrome and Churg-Strauss syndrome. Therapy in most of these clinical entities consists of long-term treatment with systemic corticosteroids, which is not always successful and has substantial side-effects. Interest has increased considerably regarding alternative corticosteroid-sparing "smart" regimens in these diseases that target IL-5, an important regulator of eosinophilic development and function. To date, two humanized monoclonal antibodies, mepolizumab and reslizumab, have been developed that bind to human IL-5. In addition a new monoclonal antibody (MEDI-563) has been recently developed targeting the IL-5 receptor. This review will investigate the current status on IL-5 targeted therapy and related patents regarding eosinophil-driven respiratory diseases, primarily eosinophilic asthma but also CSS and HES. Recent advances and information from clinical trials will be presented in a way that will allow the reader to approach the role of the eosinophil in the lung diseases presented in this review.