Purpose: This study was to examine the effects of deep breathing exercises with Incentive Spirometer on the pulmonary ventilatory function of pnemothorax patients undergoing a thoracotomy. Mothod: This experiment used anonequivalent control group non-synchronized design which compared pre-experimental measures with post-experimental ones. The subjects of this study were 34 inpatients who were scheduled for a thoracotomy and classified into the experimental group (17 patients) or control group (17 patients) by using an Incentive Spirometer or not. The collected data was analyzed by a SPSS Win I PC (percentage, mean, standard deviation, chi-square test, t-test, repeated measured two-way ANOVA). Result: The Pulmonary Ventilatory Function of the experimental and control group were significantly increased on the first day, third day, and fifth day after the thoracotomy, but the group interaction period was not significant. Conclusion: This study showed that the deep breathing exercises with an Incentive Spirometer and deep breathing exercise without an Incentive Spirometer were both effective for recovering the pulmonary ventilatory function after a thoracotomy.