The provision of health care in the United States has been described as fragmented, with patients seeing multiple providers. Fragmented care has been found to be, among other things, both costly, since provider payments are not linked to performance or outcomes and services can be duplicative, and of lower quality, since providers lack financial incentives to coordinate care. This book examines ACOs as a model of integrated care with a focus on delivery systems such as the Mayo Clinic, Geisinger Health System, Kaiser Permanente and Intermountain Healthcare. While ACOs can be designed with varying features, most models put primary care physicians at the core, along with other providers, and emphasize simultaneously reducing costs and improving quality.