Many individuals with COPD develop a lack of confidence regarding their ability to avoid breathing difficulty while participating in certain activities, however minimal the physical demands of the activity may be. This lack of confidence may be expressed as low self-efficacy. As a result of low self-efficacy, COPD patients may refrain from many routine activities of daily living. Identifying situations in which individuals with COPD experience low self-efficacy would allow the development of specific treatment interventions designed to increase the patient's self-efficacy in those situations and consequently increase activity. We developed a 34-item COPD Self-Efficacy Scale (CSES) to assess self-efficacy in individuals afflicted with COPD. The CSES has good test-retest reliability (r = .77), excellent internal consistency (Cronbach's alpha = .95), and a five-factor structure (negative affect, intense emotional arousal, physical exertion, weather/environmental, and behavioral risk factors.