Electronic medical records have the potential to determine the actual relationship between patterns of preventive and disease management care and the occurrence of disease events that this care is designed to prevent, but new approaches are needed to realize this potential. This project will refine and test a promising method for doing this; a method that can quickly, and at reasonable cost, determine what works and what does not, and also what the benefits or risks there are to following, or not following, health-care evidence-based guidelines. This information could have a profound impact on the quality of health care and it can also serve as a means to evaluate the impact and costs of alternative approaches to care.