The burden of urologic diseases on the American public is immense in both human and financial terms and until now has remained largely unquantified. Urologic diseases encompass a wide scope of illnesses of the genitourinary tract, including conditions that are congenital and acquired, malignant and benign, male and female, medical and surgical. They can occur at any point in the course of human development, from hydronephrosis in utero to urinary incontinence in the elderly. They may be acute and self-limited or chronic and debilitating, may primarily affect quality or quantity of life, and may be financially insignificant or catastrophic. Some urologic diseases present with complex signs and symptoms and require extensive evaluation, while others present with classical symptoms and are easily diagnosed. Still others occur without any symptoms at all and are discovered incidentally or during screening. For many urologic diseases the etiology is well understood, and the natural history is fairly predictable. As is the case with many organ systems, physician practice patterns for treating both common and uncommon urologic conditions vary widely and have evolved substantially during recent years. Accurate information on the epidemiology and impact of urologic diseases is critical to the equitable allocation of scarce resources at the national, state, and local levels. Indeed, as the American population ages, there is a growing need for information about the urologic health problems facing older adults. In conjunction with findings from clinical studies and basic research on biological mechanisms, an epidemiologic approach offers insights on the prevalence, etiology, and impact of urologic conditions. This information can provide the basis for planning health care services and intervention programs (1).Despite the need, reliable and valid health services data about urologic diseases have been scattered, inconsistent, and not readily available. The capabilities of the information age highlight this deficiency. There is no national surveillance system describing prevalence and incidence across all urologic diseases. Instead, various government and non-government agencies in the United States maintain a patchwork of population-based studies, observational cohorts, national interview surveys, reviews of physician practice patterns, hospital system databases, regional cancer registries, state health department health information systems, and federal, state, and private insurance claims-based datasets that can provide useful health statistics. These sources contain a wealth of epidemiologic and health services information about health care costs, access, and quality, as well as trends in the diagnosis and management of urologic diseases; however, the information sources remain largely untapped. The overall objective of this project, Urologic Diseases in America, is to quantify the burden of urologic diseases on the American public. We undertook this effort with the aid of sophisticated research methodologies and experienced analytic and administrative staff. Our team included epidemiologists, health economists, statisticians, programmers, and urologists trained in health services research. We searched all potential data sources for IntroductionMark S. Litwin, MD, MPHChristopher S. Saigal, MD, MPHUrologic Diseases in Americaxiirelevant information and health statistics in order to gather current and retrospective data on all aspects of the epidemiology, practice patterns, costs, and impact of urologic diseases in the United States. This volume is intended to convey meaningful information to users at various levels of medical sophistication, including the public, elected leaders, government officials, non-governmental organizations, media outlets, physicians, nurses, allied health care personnel, and academic researchers. We began our work by conducting an exhaustive nationwide search for all possible sources of health data for urologic diseases in America. This search included data sources such as the large population surveys maintained by the federal government (e.g., National Center for Health Statistics), health care financing agencies (e.g., Centers for Medicare and Medicaid Services), hospital consortia, insurers, physician groups, state and county medical associations, physician specialty societies, private health care foundations, private sources, and the published literature. After defining a universe of potential data sources, we assessed each one on the basis of relevance, reliability, validity, quality assurance mechanisms, accessibility, cost, user-friendliness, and other factors determined to be important to researchers and the public. With guidance from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), we selected the datasets most likely to provide useful information (Appendix A). These included datasets from the Centers for Medicare and Medicaid Services, population-based datasets, datasets with information about health care utilization and costs, and those with unique features or populations of interest that added dimension to the project.