This study, reprinted from the Journal of the American Medical Association, compares quality of care measured by explicit criteria, implicit review, and sickness-adjusted outcomes at different types of hospitals. The study included a random sample of 14,008 elderly Medicare patients hospitalized with congestive heart failure, acute myocardial infarction, pneumonia, stroke, or hip fracture. Half of these patients were hospitalized in 1981 or 1982, and half between July 1, 1985 and June 30, 1986. Samples were taken from 297 hospitals in 30 geographic areas in five states. Quality of care ratings for hospital types are similar using explicit criteria, implicit review, and outcomes adjusted for sickness at admission. Quality differences between types of hospitals were large, with the lowest group estimated to have four percentage points higher mortality than major teaching hospitals in a cohort of patients with average mortality of 16%. Quality varies from state to state, but teaching, larger, and more urban hospitals have better quality in general than nonteaching, small and rural hospitals. Hospital quality persists over time, but small nonteaching hospitals narrowed the gap with better quality hospitals between 1981 and 1986. The authors conclude that the different measures led to consistent and plausible relationships between quality and hospital characteristics. Thus, valid information about hospital quality can be obtained. We need to develop ways to use such information to improve care.