This was a retrospective cohort design using administrative claims data from Jan 1, 2003 through Sep 30, 2007, representing the years of available data, were used for this study. Managed care enrollees having at least one pharmacy claim for tiotropium (TIO) during the study period were identified as the target population. An index TIO prescription was defined as the first chronologically occurring pharmacy claim for TIO during the period Jan 1, 2004 to Aug 31, 2006, called the enrollment period. The date of the index TIO prescription was termed as the index Rx date, and the 1-year period before the index Rx date was termed as the pre-index period. The period after the index date was termed as the post-index date, and is further divided into a 30-day combination assessment period and a 1-year follow-up period. COPD clinical and economic outcomes were measured in a variable length follow up period.