The Commission on Professional and Hospital Activities (CPHA) developed the Risk-Adjusted Mortality Index (RAMI), a method for comparing hospital death rates using existing abstract or billing data. The method is comprehensive insofar as it includes all payers and all types of cases except neonates. RAMI was designed to differentiate among admissions on the basis of the patient characteristics that increase or reduce the risk of dying in the hospital. Using a large national data base, risk factors were determined empirically within each of 310 clusters based on diagnosis-related groups (DRGs). The model was very effective at predicting risk-adjusted outcomes, with a correlation of 0.98 between actual and predicted deaths in a sample of 300 hospitals. RAMI appears to be a powerful tool for using existing data to monitor changes over time in hospital death rates.