Objective:To investigate the additional effect of incentive spirometry to chest physiotherapy to prevent postoperative pulmonary complications after thoracic surgery for lung and esophageal resections.Design:Randomized controlled trial.Setting:University hospital, intensive care unit, and surgical department.Patients:Sixty-seven patients (age, 59 ± 13 yrs; forced expiratory volume in 1 sec, 93% ± 22% predicted) undergoing elective thoracic surgery for lung (n = 40) or esophagus (n = 27) resection.Interventions:Physiotherapy (breathing exercises, huffing, and coughing) (PT) plus incentive spirometry (IS) was compared with PT alone.Measurements and Main Results:Lung function, body temperature, chest radiograph, white blood cell count, and number of hospital and intensive care unit days were all measured. Pulmonary function was significantly reduced after surgery (55% of the initial value) and improved significantly in the postoperative period in both groups. However, no differences were observed in the recovery of pulmonary function between the groups. The overall score of the chest radiograph, based on the presence of atelectasis, was similar in both treatment groups. Eight patients (12%) (three patients with lobectomy and five with esophagus resection) developed a pulmonary complication (abnormal chest radiograph, elevated body temperature and white blood cell count), four in each treatment group. Adding IS to regular PT did not reduce hospital or intensive care unit stay.Conclusions:Pulmonary complications after lung and esophagus surgery were relatively low. The addition of IS to PT did not further reduce pulmonary complications or hospital stay. Although we cannot rule out beneficial effects in a subgroup of high-risk patients, routine use of IS after thoracic surgery seems to be ineffective.