Performance measurement in surgery is required for quality improvement. Most quality measures have focused on processes of care, but outcomes are generally considered the bottom line of health care quality. Colon surgery is a common surgical procedure and is associated with appreciable morbidity and mortality, making it an ideal target for outcomesbased surgical quality improvement efforts. Therefore, The American College of Surgeons sought to develop a colectomy composite outcome measure for mortality or any serious morbidity. This measure, now endorsed by the National Quality Forum, is feasible, is valid, has substantial clinical importance, and is projected to have acceptable reliability for 84% of colon resections performed in the United States.