At the very heart of modern healthcare is a critical paradox. Today, as never before, healthcare has the ability to enhance the quality and duration of life. At the same time, healthcare has become so enormously costly that it can easily bankrupt governments and impoverish individuals and families. According to federal forecasters, by the year 2015 one in every five U.S. dollars will be spent on healthcare, for total annual healthcare spending of more than $4 trillion. While the cost of healthcare is going up, the number of individuals and families without health insurance coverage is increasing. For many, the miracles of modern medicine may be unaffordable. Health services research investigates the relationship between the factors of cost, quality, and access to healthcare and their impact upon medical outcomes (i.e., death, disease, disability, discomfort, and dissatisfaction with care). Health services research addresses such key questions as, Why is the cost of healthcare always increasing? How can healthcare costs be successfully contained without jeopardizing quality? How can medical errors be eliminated? What is the medical impact of not having health insurance coverage? The proposed encyclopedia addresses these and other important questions and issues.