PURPOSE: Exercise is an important treatment modality for persons with chronic obstructive pulmonary disease (COPD), but factors influencing adherence have been examined infrequently. The purpose of this investigation was to explore adherence factors to a progressive resistance exercise program for persons with COPD. METHODS: Persons with COPD enrolled in a 12-week trial of progressive resistance exercise were invited to participate in 2 semistructured qualitative interviews exploring program adherence. Interviews were audio-taped, transcribed, and then coded independently by 2 researchers. Themes relating to short-term and long-term adherence were then developed and described. RESULTS: Twenty-two participants were interviewed at the conclusion of the intervention (12 weeks), and 19 completed a second interview at 24 weeks. Short-term exercise adherence was facilitated by expected outcomes, self-motivation, supervision, and group support, whereas health and weather factors were the major barriers to adherence. The barriers to exercise remained unchanged at 24 weeks despite a large decline in exercise adherence. Removal of environmental support at 12 weeks may have contributed to poor long-term exercise maintenance, with participants identifying group support and regular monitoring by a therapist as the most important strategies for maintaining exercise. CONCLUSIONS: The provision of external support in training program design appears important for persons with COPD. Longer-term adherence declined when group support and regular monitoring by a therapist was removed, despite the major perceived exercise barriers remaining unchanged. Therefore, further investigation is required to determine effective strategies for maximizing longer-term exercise adherence in this population.