We present results from the first phase III trial of once-daily tiotropium add-on to inhaled corticosteroids (ICS) plus one or more controller therapies in adolescents with severe symptomatic asthma.In this double-blind, parallel-group trial (NCT01277523), 392 patients aged 12-17 years were randomised to receive once-daily tiotropium 5 µg or 2.5 µg, or placebo, as an add-on to ICS plus other controller therapies over 12 weeks. The primary and key secondary end-points were change from baseline (response) in peak forced expiratory volume in 1 s (FEV1) within 3 h post-dosing (FEV1(0-3h)) and trough FEV1, respectively, after 12 weeks of treatment.Tiotropium 5 µg provided numerical improvements in peak FEV1(0-3h) response, compared with placebo (90 mL; p=0.104), and significant improvements were observed with tiotropium 2.5 µg (111 mL; p=0.046). Numerical improvements in trough FEV1 response and asthma control were observed with both tiotropium doses, compared with placebo. The safety and tolerability of tiotropium were comparable with those of placebo.Once-daily tiotropium Respimat add-on to ICS plus one or more controller therapies in adolescents with severe symptomatic asthma was well tolerated. The primary end-point of efficacy was not met, although positive trends for improvements in lung function and asthma control were observed.