To determine the extent to which patients with Stage I COPD experience improvements in physical performance and quality of life as a result of exercise training, and to compare these improvements with those seen in Stage I and II patients, 151 patients with COPD underwent a 12-wk exercise program. Outcomes were measured at baseline and follow-up. Physical performance was evaluated by means of a 6-min walk, treadmill time, an overhead task, and a stair climb. General health-related quality of life was assessed in terms of the domains of Social Function, Health Perceptions, and Life Satisfaction. Disease-specific health-related quality of life was assessed with the Chronic Respiratory Disease Questionnaire (CRQ). Six-minute walk distance increased significantly in Stage I (200.5 ft [95% CI: 165.4, 235.7]), Stage II (238.3 ft [143.3, 333.3]), and Stage III (112.1 ft [34.6, 189.6]) participants. Treadmill time increased significantly in Stage I (0.42 min [0.20, 0.64]) and Stage II (0.64 min [0.14, 1.4]) participants. Time to complete the overhead task decreased significantly in Stage I (0.91 s [1.72, 0. 11]) and Stage II (1.39 s [2.66, 0.13]) participants. None of the measures of general health-related quality of life improved in any of the three groups. Participants in Stages I, II, and III all experienced improvements in the CRQ domains of dyspnea (0.72 [0.53, 0.91], 0.47 [0.02, 0.91], and 0.46 [0.05, 0.87], respectively) and fatigue (0.49 [0.33, 0.66], 0.54 [0.20, 0.87], and 0.55 [0.05, 1.05], respectively). These results suggest that all patients with COPD will benefit from exercise rehabilitation. Berry MJ, Rejeski WJ, Adair NE, Zaccaro D. Exercise rehabilitation and chronic obstructive pulmonary disease stage.