Who's the best bronchodilator on the block? In 725 centers, in 25 countries, among COPD'ers with FEV1<=70% (moderate-or-worse) and an exacerbation in the past year, after using tiotropium or salmeterol (double-dummy) for 1 year, the winner is.... Tiotropium ... probably! With a time-to-first-exacerbation of 187 vs. 145 days -- but only in the quartile of study patients having the earliest exacerbations. That sounded confusing to us too. Only 36% of patients had an exacerbation during the year, so this is really an analysis of the first 1,844 to have exacerbations of the original 7,376 patients (if our math is right -- they don't provide this number). That said, tiotropium won hands down, with a small/modest benefit that was not apparently influenced by glucocorticoid use, drug discontinuation or other confounders. In absolute terms, tiotropium prevented 0.08 more exacerbations per patient per year (0.64 vs. 0.72) than did salmeterol, especially severe exacerbations (number needed to treat for one year to prevent an additional exacerbation = 13). No difference in adverse events. Boehringer Ingelheim was heavily involved in the design and controlled the statistical analysis of the study. (n=7,376). NEJM 2011;364:1093-1103.