Nineteen patients with giant bulla were followed for more than 1 year after bullectomy. They were divided into two groups according to their postoperative symptoms. Group 1 consisted of 16 patients who had no problems in their postoperative clinical course, while Group 2 included 3 patients who complained of severe dyspnea at 5 to 6 years of follow-up. Prior to operation, the forced expiratory volume in 1 sec over vital capacity (FEV1%) was 66.8 +/- in Group 1 and 27.6 +/- 5.4% in Group 2. Differences in preoperative and postoperative FEV1% were statistically significant within Group 1 and between the two groups. Postoperative FEV1% (Y) correlated significantly with preoperative FEV1% (X) (Y = 0.74X + 25.4; r = 0.836; p less than 0.001). Thus, we were able to predict the postoperative FEV1% from the preoperative value. Regional ventilation over volume was computed from the washout curve of xenon 133 after reaching equilibrium with rebreathing in a closed circuit (V/V dynamic). Group 2 had significantly lower regional ventilation over volume in all regions, both before and even after bullectomy, compared with normal subjects or Group 1 patients. Preoperative V/V dynamic was below 0.5 in all regions of Group 2. Furthermore, postoperative V/V dynamic (Y) correlated significantly with preoperative V/V dynamic (X) in the upper region (Y = 0.46X + 0.40; r = 0.638; p less than 0.02) and in the lower region (Y = 0.72X + 0.33; r = 0.869; p less than 0.001). We conclude that functional indications of bullectomy for giant bulla are that FEV1% should be greater than 40%, and that regional V/V dynamic should be greater than 0.5. On the other hand, symptomatic and functional improvement following bullectomy was reduced in patients whose FEV1% was less than 35% in whose V/V dynamic was remarkably disturbed in all regions of the involved hemithorax.