Background A pharmacokinetic study in an Asian population showed that tiotropium 5 μg via Respimat leads to the same plasma levels compared to 18 μg via HandiHaler.The objective of the trial was to compare the efficacy and safety of longterm treatment (1 year) with tiotropium bromide (5 μg) via Respimat（R） with placebo in patients with chronic obstructive pulmonary disease (COPD).Methods A total of 3991 patients were randomized in this double-blind,placebo controlled,parallel group study,while in China 338 patients (309 males,29 females) received either tiotropium bromide (n=167) or placebo (n=171).Tiotropium bromide solution or matching placebo was delivered via Respimat（R） at a dosage of 5 μg (2 x 2.5 μg/puff) once daily for 48 weeks.Co-primary endpoints were trough forced expiratory volume in one second (FEV1) and the time to first exacerbation.Results Statistically significant improvements in trough FEV1 and trough forced vital capacity (FVC) in the tiotropium group were achieved at weeks 4,24,and 48 compared with those in the placebo group.A statistically significant difference (P=0.0027) in favour of tiotropium was also observed for the time to first exacerbation.The total numbers of exacerbations during treatment were 90 and 128 in the tiotropium and placebo groups,respectively,with a rate ratio of 0.69 (P=0.0164).The difference between the treatment groups in the adjusted mean changes from baseline of St.George Respiratory Questionnaire (SGRQ) total score was-3.9 (95％ Cl:-7.5,-0.2) and was of statistical significance (P=0.0367).The incidences of serious adverse events (SAEs) in the tiotropium and placebo groups were 16.2％ and 17.0％,respectively.Seven deaths occurred whilst patients were on treatment,four in the tiotropium group and three in the placebo group,all of which were assessed as non-related study drugs by the investigators.Conclusions Tiotropium significantly improved lung function and quality of life,delayed the time to first exacerbation,reduced the number of exacerbations.Overall,tiotropium was well tolerated.