This was a retrospective cross-sectional database study using administrative data (study period: 1/1/2003 through 7/31/2008). Managed care enrollees (aged >40 years) having at least one Hospitalization with primary or secondary diagnosis of COPD (ICD code 491.xx, 492.xx and 496.xx) or at least one Emergency Room (ER) visit with primary diagnosis of COPD (index event) during the study period was the target population. All subjects were required to have one year of pre-index period baseline data. COPD events of interest were ER, Hospital and physician visits followed by oral corticosteroids (OCS) or antibiotics (Ab) within 7 days. Other censoring events were treatment switch; loss of enrollment; >60-day gap between medication fills; or end of study period.