It is known that a pulmonary rehabilitation program improves dyspnea and exercise tolerence in patients with chronic obstructive pulmonary disease. However, it is also known that although it does not improve pulmonary function. This study was performed to evaluate the effect of a 4 week pulmonary rehabilitation on pulmonary function, gas exchange, and exercise tolerance in patients with chronic obstructive pulmonary disease. The pulmonary rehabilitation programs included breathing exercises, such as pursed-lip breathing and diaphragmatic breathing, upper-limb exercises, and inspiratory muscle training. These activities were performed for 4 weeks in twenty one patients with chronic obstructive pulmonary disease. Pre and post-rehabilitation pulmonary function and exercise capacities were compared after the 4 week period. Results are as follows: 1) Before the rehabilitation, the predicted value of FVC and FEV1 of the patients were 70.3$pm$16.7% and 41.1$pm$11.9% respectively. These pulmonary functions did not change after pulmonary rehabilitation. 2) Aloility of walking a 6 minute distance (325.29$pm$122.24 vs 363.03$pm$120.01 p=.01) and dyspnea (p=.00) were significantly improved after rehabilitation. Thus showing that pulmonary rehabilitation for 4 weeks can improve exercise performance and dyspnea in patients with chronic obstructive pulmonary disease.