Pulmonary complications are the main source of postop erative morbidity and mortality, with respiratory failure and pneumonia resulting in 50% of postoperative deaths after lung surgery. Despite the high incidence of postop erative complications, pulmonary resection remains the only effective treatment for lung cancer. Substantial resources are ascribed for the perioperative care of these high-risk patients. Clinical experience would dic tate that predicting outcome could be of immense value in allocating resources. This review will consider the predictive value of preoperative testing, including spi rometry, split lung function, blood gas analysis, carbon monoxide diffusion capacity, pulmonary vascular resis tance, and exercise testing, as well as recent efforts to develop a combined cardiopulmonary index.