During the past several years, one of the most perplexing issues for surgeons has been the assessment of quality of care. We, however, owe it to ourselves and our patients to master the substantive issues that underlie current discussions about this subject. What is quality care? Many definitions have been proposed. Donabedian developed the classic triad for measuring quality in health care: structure, process, and outcome. Structural data are characteristics of physicians and hospitals (eg, specialty of physicians, ownership of hospitals). Process data result from an interaction between physician and patient (eg, tests ordered). "Outcome" refers to the subsequent health status of the patient (eg, improvement in gastrointestinal function). To be credible, structure and process must lead to differences in outcome, and outcome data, to be valid, must show that differences will result if processes of care, under the control of the provider, are modified. There are critics of each approach. When used appropriately, both process and outcome measures can provide important information about the quality of care. We, as surgeons, rely heavily on outcome data. In 1990, the Institute of Medicine defined quality as: "The degree to which Health Services for individuals and populations increase the likelihood of desired health outcomes and are consistent with current professional knowledge." Most agree with this definition and feel it can be measured with a degree of accuracy comparable with that of most measures used in clinical medicine.