In the United States, the quality of care for chronic conditions such as diabetes is very poor.1,2The Chronic Care Model, the best available theoretical model of how health care should be delivered, offers a framework for how it can be improved.3,4One of the central features of the model is the use of registries to feed back organizational or health care provider performance to improve quality of care. Are registries a good idea? Who should maintain them? How should they be used? Which patients should be included?