OBJECTIVES: This retrospective study quantifies the prevalence of insomnia among patients with chronic obstructive pulmonary disease (COPD) from a large outpatient database. COPD is an umbrella term for the lung disease category associated with airflow obstruction, which includes emphysema, chronic bronchitis, and chronic asthma, either alone or in combination. METHODS: Data from April, 1996 to September, 2003 on patients with a diagnosis of COPD (ICD-9 codes 491.2, 492.0, 492.8, 493.2, and 496) were extracted from the GE Medical Systems database—a large, outpatient, multipractice electronic database system with input from over 2000 practicing physicians in 26 US states. The insomnia cohort was defined as patients having either a diagnosis consistent with insomnia (ICD-9 codes 307.4x [x=1-2, 9] and 780.5x [x=0, 2] or a prescription for insomnia medication. Demographic characteristics, comorbid conditions, and concomitant medications were evaluated. RESULTS: A total of 5,777 (21.4%) of 27,052 patients in the COPD cohort were identified as having a diagnosis and/or being treated for insomnia, compared with 7.2% of the non-COPD patients. CONCLUSIONS: This exploratory analysis revealed that patients with COPD in this large outpatient database were diagnosed with and/or treated for insomnia almost three times as frequently as those patients not having a diagnosis of COPD. These data suggest that insomnia is a common and clinically important comorbidity associated with COPD. The nature of this association should be further investigated with a well-designed prospective study, and treatments for insomnia related to COPD need to be examined in greater detail.