Health care in America is plagued by extensive gaps in quality. Too often care provided to patients does not match what the medical community has determined to be the most effective care. Abundant research has shown that these gaps in quality are responsible for increased costs, wasteful and ineffective care, preventable complications, avoidable hospitalizations, decreased quality of life, disability, and premature death. The National Healthcare Quality Report (NHQR) and National Healthcare Disparities Report (NHDR), published annually by the Agency for Healthcare Research and Quality since 2003, provide both extensive research and data on the extent of health care quality gaps as well as national benchmarks for quality. This Resource Guide and its accompanying Workbook draw on the NHQR and the NHDR to support State-level efforts to improve the quality of asthma care. This Resource Guide is designed to help State leaders identify measures of asthma care quality, assemble data on asthma care, assess areas of care most in need of improvement, and learn what other States have done to improve asthma care. Taken together, the Resource Guide and its companion Workbook can help State leaders to develop an asthma quality improvement action strategy. Asthma is a chronic lung condition that impairs normal breathing. The disease affects a growing number of Americans. In 2003, nearly 30 million people had been diagnosed with asthma at some point in their lives and nearly 20 million people stated they currently had asthma (Centers for Disease Control and Prevention, 2002a). Asthma is also costly: total estimated costs in 2001 were $14 billion (American Lung Association, 2004). For several reasons, asthma presents an opportune target for quality improvement: Increased prevalence, especially among children and adolescents; Disparities between socioeconomic groups and between racial/ethnic groups in terms of diagnoses and quality of asthma care; A range of interventions and treatment that can successfully control the disease and prevent attacks; High health care costs of uncontrolled asthma and the potential for a positive return on investment for purchasers and the health care system as a whole through asthma quality improvement. Improved quality of asthma care may help to cut costs, reduce disparities, and improve the quality of life for millions of people with asthma.