Patients undergoing elective surgery first need to be screened for operative risks by reviewing factors that relate to the patient and factors that relate to the procedure they are undergoing. The identification of high-risk patients undergoing high-risk procedures may be aided by reviewing the following factors: the presence of symptomatic lung disease, smoking, obesity, abnormal blood gas values, spirometry, and presence of sleep apnea. The more risk factors a patient has, the more likely the patient will develop postoperative complications. Further risk stratification may be accomplished by means of exercise testing, either through formal cardiopulmonary exercise testing or through symptom-limited stair climbing. When high-risk patients are identified, preoperative therapy aimed at reducing overall postoperative morbidity and mortality may help decrease the risk to a minimum.