The discriminant function (Z) for predicting postoperative performance status in patients with giant bulla was addressed in our previous paper. In the present study, patients with dyspnea were classified into Group 1 or Group 2 based on preoperative function, Group 1 showing continuous improvement in dyspnea and Group 2 unchanged or worsened condition after bullectomy. Of the 47 patients in this study, 28 had dyspnea of grade 2 or more, 19 revealing no symptoms prebullectomy. The group predictions for the 28 patients were compared with the postoperative status in dyspnea for over four years following surgery. The predicted grouping in 26 of the 28 (93%) agreed with the postoperative status but in two it did not: one was familial bullous emphysema the other had repeated episodes of pneumonia, both of which were predicted for Group 1. All 19 patients without preoperative dyspnea were studied their symptoms and lung functions before and after bullectomy. After surgery, none showed dyspnea and significant changes of functions. As to preoperative pulmonary function, patients with FEV1.0% of more than 60% and delta N2 of less than 2% were improved, the prediction agreeing with the actual results. Fourteen patients with FEV1.0% of less than 55% showed high delta N2. When delta N2 exceeded 3.5%, deterioration of dyspnea was observed following surgery. Bullectomy is indicated in patients with low pulmonary function, by preoperative FEV1.0% and delta N2.