To control rising health care costs, the federal government, in 1983, established a prospective payment system (PPS) to reimburse hospitals for inhospital care of Medicare patients. PPS changed the way Medicare reimbursed hospitals from a cost or charge basis to a prospectively determined fixed-price system in which hospitals are paid according to the diagnosis-related group (DRG) into which a patient is classified. This report constitutes the executive summary of an evaluation of the impact of the DRG-based PPS system. Six conditions were selected for the evaluation: congestive heart failure, acute myocardial infarction, hip fracture, pneumonia, cerebrovascular accident, and depression. The authors used both explicit and implicit measures to assess quality of care. Two key policy conclusions emerge from the findings: (1) at least through the middle of 1986, PPS did not interrupt a long-term trend toward better hospital care; and (2) PPS has had a detrimental effect on patients' stability at discharge. The authors recommend that physicians, hospitals, and professional review organizations undertake a more systematic assessment of a patient's readiness to leave the hospital, and that clinically detailed data on sickness at admission, processes, discharge status, and outcomes continue to be collected regularly as long as PPS is in place.