SIENA (Steroids in Eosinophil Negative Asthma) was a clinical trial for adolescents and adults with mild to moderate asthma. The purpose of this study was to find out what medications work best for patients with different types of asthma. In this trial, we tested whether people benefit from taking an inhaled corticosteroid (fluticasone propionate) versus a long-acting muscarinic antagonist (tiotropium) based on the type of inflammatory cells in their airways. The study involved 9-12 clinic visits over 1 year (about 1 visit per month) during which participants took inhalers provided by the clinical trial and kept track of their asthma symptoms using an electronic diary (“e-diary”). SIENA was sponsored by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH). The SIENA study has been completed.