Registries of patients with particular conditions or who have received a particular treatment have a long history and are widely used in many countries. This paper focuses on two kinds of registries for patients with diabetes and for those who have received a joint hip replacement in Sweden and England. These examples illustrate how registries can serve multiple purposes, including providing quality and safety feedback to providers and purchasers, generating planning data for health systems, evaluating guidelines, and performing outcomes research. While registries are not foreign to the United States, the completeness and accomplishments of Sweden and Englands registry system go well beyond the American experience, and show how more can be done to make use of these valuable tools.