Given both the high-risk nature of the critical limb ischemia (CLI) patient population, as well as the variety of available treatment options, the ability to use preprocedure variables to predict a given outcome has become increasingly important. The three main advantages associated with accurate risk stratification include: (1) improved clinical decision-making based on realistic patient and physician expectations, (2) ability to benchmark individual practitioners and institutions by comparing their outcomes with expected outcomes specific to the actual patients being treated, and (3) creation of objective performance goals for the evaluation of new treatment modalities in specific patient populations. Patients with CLI have multiple comorbidities that can impact greatly on the outcomes of attempted revascularization. The PREVENT III CLI Risk Score was developed as a tool to estimate amputation-free survival at 1 year in patients undergoing vein bypass surgery for limb salvage, and has now been validated using data from >3,000 cases. The score incorporates five baseline clinical variables-dialysis, tissue loss, age, hematocrit, and coronary artery disease-and assigns patients into three distinct risk groups. Patients in the high-risk subgroup (8.2% of total number of patients evaluated) experienced <50% amputation-free survival at 1 year. This tool may be valuable in assisting both the surgeon and patient faced with treatment decisions in CLI.