The aim of preoperative risk analysis is to reduce postoperative morbidity and mortality by identification of compromised organ function which can be improved by targeted preoperative measures and problem-oriented postoperative therapy. Ideally, therefore, preoperative risk assessment, influences the timing of the surgical procedure, the choice of the surgical approach, and the postoperative management. Identification of preexisting relevant disorders that may influence the postoperative course is an essential prerequisite of risk analysis. While preoperative risk analysis today gains in importance with the increasing extent of elective surgical procedures, preoperative risk evaluation still plays a minor role in the emergency situation when the given patient-dependent risk usually has to be accepted. Objective risk evaluation depends on the general and nutritional status, the pulmonary, cardio-vascular, hepatic, and renal function, and the cooperation of the patient. These factors, however, clearly have to be seen in relation to the type and extent of the planned surgical procedure. The selection of additional tests of organ function, exceeding the standard tests required prior to any surgical intervention, must be guided by the extent of the planned surgical procedure, the physiologic alterations associated with the surgical procedure, and the suspected underlying organ dysfunction. Generally accepted multi-factorial classification systems to identify patients at risk for a wide spectrum of surgical procedures are currently not available. Using the model of esophagectomy in patients with esophageal cancer we could, however, demonstrate that a quantitative assessment of the peri- and postoperative risk based on preoperatively available physiologic parameters is possible and markedly reduces postoperative mortality when applied prospectively. The development and validation of similar risk-score systems for other surgical procedures should be considered.