The US health care industry increasingly agrees that sharing information about quality of care is necessary to stimulate providers' efforts to improve the quality of health care. The availability of mandated, uniform clinical data in all nursing homes and home health agencies has facilitated the rapid adoption of public reporting of comparative quality data. This paper examines the conceptual and technical challenges underlying the application of information about long-term care provider quality to judge and compare the quality of care provided by nursing homes and home health agencies. In general, the impetus to apply the emerging set of quality "tools" based on mandated clinical assessments may have outstripped the evidence for their valid application in selecting top providers or for rewarding their superior performance.