We are developing a decision support tool to help clinicians and policy makers estimate the impact of various coronary heart disease (CHD) treatments on disease outcomes for populations. We have created seven modules that correspond to states commonly encountered with CHD, that is, congestive heart failure, tachyarrhythmia, stable angina pectoris, acute coronary syndrome, bradycardia, postmyocardial infarction, and postcoronary artery bypass grafting, and a healthy individual module. Within each module, we created event-decision- intervention-outcome flow pathways to simulate risk of a clinical event and the expected outcome as the result of a particular intervention. We will combine disease state probability estimates based on the experience of the Olmsted County, Minnesota, population and estimates of intervention efficacy based on clinical trial data to estimate the impact of interventions on a population. We plan to make this tool available to the public through the internet.