Although difficult to precisely define, health care quality is often measured by components of structure, outcomes, and process. One way for thoracic surgeons to evaluate their practices is to compare themselves with evidence-based national guidelines. Outcomes data are often generated from entries into large patient databases. The largest examples of these databases include the STS National Databases and the VA/ACS NSQIP programs. Each of these has unique features, but there is the common goal of enabling participants to examine their surgical outcomes and results relative to others. The data integrity of these databases is high. The new STS composite quality score for CABG combines providers' outcome and practice data into a calculated index for comparison with national averages. In addition to providing meaningful information regarding surgical outcomes and quality, these databases are used as the basis for risk-adjusted models to accurately predict surgical morbidity and mortality. These models can be used as auditing tools against which surgeon- and site-specific morbidity and mortality can be compared with predicted values. As practices and methods continue to evolve, measures of quality--and therefore quality itself--will continue to improve, resulting in better patient care.