The National Healthcare Quality Report (NHQR) is a comprehensive national overview of the quality of health care in the United States. It is a companion report to the National Healthcare Disparities Report (NHDR), which is a comprehensive national overview of disparities in health care affecting racial, ethnic, and socioeconomic groups and priority populations. The 2005 NHQR presents the third annual opportunity to measure the Nation's health care quality and to track trends over time-the primary intent of Congress's mandate to the Agency for Healthcare Research and Quality (AHRQ) to produce the NHQR. The NHQR is built on 179 measures assembled across four dimensions of quality-effectiveness, patient safety, timeliness, and patient centeredness. This year's report focuses on the state of health care quality for a group of 46 "core" report measures which represent the most important and scientifically credible measures of quality for the Nation, as selected by the Department of Health and Human Services (HHS) Interagency Work Group. The distillation of 46 core measures for the 2005 report provides a more readily understandable summary and explanation of the key results derived from the data. Also included in the report are four new composite measures, which summarize data from a collection of individual measures. Composite measures were created for heart attack, heart failure, pneumonia, and patient centered care, in addition to an overall measure of the state of health care quality improvement. Four themes that emerge from the 2005 NHQR extend the meaning of those from the 2003 and 2004 reports and add new dimensions on understanding change over time: Health care quality continues to improve at a modest pace across most measures of quality; Health care quality improvement is variable, with notable areas of high performance; Health care quality is improving, but more remains to be done to achieve optimal quality; Sustained rates of quality improvement are possible.