In the past decade, diabetes mellitus (DM) has reached epidemic proportions in the U.S. The disease now affects more than 17 million people nationwide. Include undiagnosed cases and individuals with impaired glucose tolerance, and one in every seven Americans either has diabetes, or is at high risk for developing the disease. Equally disturbing, the prevalence of diabetes has increased by 60% since 1991, and there is a direct correlation with the increase in obesity over the same period. As a result, diabetes is likely to pose a major public health problem for decades to come. The past decade also has played witness to major advances in diabetes care, beginning with the publication of the Diabetes Control and Complications Trial (DCCT) in 1993, followed by the United Kingdom Prospective Diabetes Study (UKPDS) trials in the second half of the 1990s. These studies clearly demonstrated that aggressive management of hyperglycemia significantly improves quality of life, while reducing morbidity and mortality. Effective treatment strategies also have been developed for the control of diabetes' principal comorbid conditions, hyperlipidemia and hypertension, and for the screening and early treatment of complications such as retinopathy, neuropathy, nephropathy, and foot disease. To bring data to bear on the quality improvement opportunities cited by the Institute of Medicine (IOM) in its 2003 report, Priority Areas for National Action: Transforming Health Care Quality, the Agency for Healthcare Research and Quality (AHRQ) engaged the Stanford-UCSF Evidence-based Practice Center (EPC) to analyze the scientific literature on quality improvement strategies for some of the 20 disease and practice priorities named in the IOM Report. The resulting investigations focus on translating research into practice-identifying those activities that increase the rate at which practices known to be effective are applied to patient care in real world settings. In other words, the EPC research effort aims to help narrow the "quality gap" that is in large part responsible for suboptimal health care practices and outcomes. In addition to furthering the IOM's quality agenda, this analysis also has been prepared in support of the National Healthcare Quality Report (NHQR). In this, the second volume of the Closing the Quality Gap series, the authors focused on quality improvement in the management of patients with diabetes mellitus (Type 2 diabetes), which accounts for more than 90% of diabetes cases in the U.S. Quality improvement targets included measures of disease control and provider adherence. In this review, the literature on quality improvement for diabetes care has been carefully synthesized in an effort to address three questions: 1. Are there QI strategies that improve physicians' treatment of diabetes and its comorbidities? Can the control of hyperglycemia, hyperlipidemia, and hypertension be improved? Can microvascular and macrovascular complications be prevented? 2. Are there QI strategies that improve provider adherence to recommended monitoring? Which interventions improve physicians' adherence to long-term glucose monitoring, to screening for hyperlipidemia and hypertension, and to screening for complications such as retinopathy, neuropathy, and nephropathy? 3. Are there QI strategies that improve patients' adherence to treatment and self-care measures? For more information regarding the origins and details of the research framework developed for the Closing the Quality Gap series, the statistical tools and analytical processes used throughout, and the target audiences expected to benefit most from the series, please refer to Volume 1-Series Overview and Methodology.