Clinical decision making in patients with chronic disease is hampered by the absence of reliable predictions on which to base management decisions. Using the experience accumulated in over 12 years of managing patients with coronary heart disease we have developed prediction strategies which retrospectively appear to make better estimates than the best clinicians. The purposes of this proposal are twofold. First, we wish to validate prospectively, experience-based predictions of coronary heart disease severity and prognosis and compare the accuracy of these predictions to those make by the patients' physicians. We propose to do this in a group of patients similar to those in whom the estimates are based, as well as in a different population of patients in whom we would like to apply the predictions to improve the clinical decision making process. Secondly, we want to validate for individual patients referred for noninvasive testing, pretest estimates of the diagnostic and prognostic value of the tests. We believe that if successful, we will validate both an improved clinical decision making process for patients with coronary heart disease, as well as the methodology for applying previous experience to improve clinical decision making in patients with chronic diseases.