Many published instruments are available for determining short- and long-term risk for reinfarction, stroke, and mortality. To demonstrate the clinical usefulness of estimating both cardiovascular and bleeding risk before prescribing warfarin, we chose clinical examples of low-, medium-, and high-risk patients. We derived our estimates of the rates for recurrent myocardial infarction and stroke for patients receiving aspirin by using the computed hazard ratios from a large population-based study of 2700 patients surviving hospitalization after a first myocardial infarction and followed for an average of 3.4 years (26). We chose this study for its large size, long follow-up period, emphasis on easily measured clinical predictors, and inclusion of stroke as an outcome. The following variables were associated with increased risk for recurrent myocardial infarction and stroke: age, treated diabetes, chronic congestive heart failure, angina, and serum creatinine level greater than 123.76 µmol/L (>1.4 mg/dL). We created examples of low-, medium-, and high-risk patients by applying the hazard ratios for specific risk variables to a baseline risk of 49 per 1000 patient-years of observation. Infarction rates per 1000 patient-years were 40 for a low-risk patient (no risk factors), 82 for a medium-risk patient (for example, diabetes and serum creatinine level >123.76 µmol/L [>1.4 mg/dL]), and 188 for a high-risk patient (for example, diabetes and congestive heart failure). Stroke rates for the same patients were 13, 32, and 79, respectively. Other risk stratification tools, based on the Thrombolysis In Myocardial Infarction (TIMI II) (27), Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto miocardico (GISSI) (28), Secondary Prevention Reinfarction Israeli Nifedipine Trial (SPRINT) (29), or Global Registry of Acute Coronary Events (GRACE) (30) studies, produce similar ranges of low-, medium-, and high-risk patients. A detailed calculator based on the GRACE model is available at http://www.outcomes-umassmed.org/grace.