Over the past decade, there has been an increasing awareness that the quality of medical care delivered in the United States is variable. In its seminal document dedicated to characterizing deficiencies in delivering effective, timely, safe, equitable, efficient, and patient-centered medical care, the Institute of Medicine described a quality “chasm”.1 Recognition of the magnitude of the gap between the care that is delivered and the care that ought to be provided has stimulated interest in the development of measures of quality of care and the use of such measures for the purposes of quality improvement and accountability. Consistent with this national focus on healthcare quality, the American College of Cardiology Foundation (ACCF) and the American Heart Association (AHA) have taken a leadership role in developing measures of the quality of care for cardiovascular disease (CVD) in several clinical areas Table 1. The ACCF/AHA Task Force on Performance Measures was formed in February 2000 and was charged with identifying the clinical topics appropriate for the development of performance measures and assembling writing committees composed of clinical and methodological experts. When appropriate, these committees include representatives from other organizations with an interest in the clinical topic under consideration. The committees are informed about the methodology of performance measure development and are instructed to construct measures for use both prospectively and retrospectively, rely upon easily documented clinical criteria, and where appropriate, incorporate administrative data. The data elements required for the performance measures are linked to existing ACCF/AHA clinical data standards to encourage uniform measurements of …