BACKGROUND: Tiotropium, a once-daily long-acting anticholinergic bronchodilator, has demonstrated efficacy in patients with asthma who were symptomatic despite treatment with medium- to high-dose inhaled corticosteroids (ICS). OBJECTIVE: The objective of this study was to evaluate the efficacy and safety of once-daily tiotropium Respimat (5 μg or 2.5 μg), compared with placebo Respimat, as add-on therapy to low- to medium-dose ICS for adults with symptomatic asthma. METHODS: A phase III, double-blind, placebo-controlled trial was conducted (NCT01316380). Adults with symptomatic asthma receiving low- to medium-dose ICS (200-400 μg budesonide or equivalent dose) and a pre-bronchodilator forced expiratory volume in 1 second (FEV1) ≥60% and ≤90% of predicted normal were randomized to 12 weeks of treatment with once-daily tiotropium Respimat 5 μg or 2.5 μg, or placebo Respimat, as add-on therapy to ICS. The primary endpoint was peak FEV1(0-3h) response. RESULTS: In total, 464 patients were randomized (61% female; mean age 43 years; mean baseline FEV1 78% of predicted normal). After 12 weeks, both tiotropium Respimat doses were superior to placebo (adjusted mean difference from placebo: 5 μg, 128 mL; 2.5 μg, 159 mL; both P < .001). Both doses of tiotropium Respimat were also superior to placebo with regard to the secondary endpoints of adjusted mean trough FEV1 and FEV1 area under the curve(0-3h) responses, and the other endpoints of morning and evening peak expiratory flow. Adverse events were comparable across the treatment groups. CONCLUSIONS: Once-daily tiotropium Respimat add-on therapy to low- to medium-dose ICS in adults with symptomatic asthma is an efficacious bronchodilator, and its safety and tolerability are comparable with those of placebo Respimat.