The aim of the present investigation was to evaluate which parameters of preoperative spirometry, arterial blood gas, radionuclide lung scanning and cardiopulmonary exercise test are the best predictor of postoperative morbidity and mortality in patients submitted to pneumonectomy. The study was conducted in 150 patients (mean age, 57.1). Forty-four patients (29.3%) had postoperative complications. Four patients (2.7%) died within one month of the pneumonectomy. Patients with complications had significantly lower ppoFEV1 as percentage of predicted and lower VO2 max, and those who died also had a significant decrease in PaO2 during exercise. Moreover, among patients with obstructive pulmonary disease (FEV1<70% of predicted), we found a significantly higher percentage predicted residual volume and a significantly lower VO2 max in complicated patients. The present data support the suggestion that exercise testing could be a useful adjunct in the evaluation of postoperative risk for pneumonectomy, especially in patients with obstructive pulmonary disease. In particular, patients with VO2 max <50% of predicted should be considered at high risk of morbidity from cardiopulmonary causes.