Some would say that the beginning of wisdom in health services research is the realization that what cannot be measured cannot be changed. Until recently, we lacked a single, accessible source of national longitudinal data on health care quality and disparities related to race, ethnicity, and socioeconomic status. Along with the rest of the health services research community, we at the Agency for Healthcare Research and Quality (AHRQ) knew all too well the frustrations and limitations on research caused by the lack of such data.Since the release of AHRQs first National Healthcare Quality Report (NHQR) and National Healthcare Disparities Report (NHDR) in December 2003, AHRQ has been working to resolve this dilemma.