The quiescent interest in understanding the variations in the quality of hospital care has been revitalized recently with the government's release of hospital-specific mortality data. The authors reviewed all published studies that either named hospitals and gave their death rates or explored which of their characteristics explained the differences in their rates. The literature is only in fair condition. It is sparse and flawed, and, before the government's release, did not identify an individual hospital's mortality experience by name. Twenty-two studies were analyzed; only five (23%) met criteria for validity. Seventeen (77%) focused on in-hospital mortality. Data were collected for a short time, were not gathered uniformly, and came from a sample of local hospitals. Researchers identified and explained limitations in their studies and were particularly concerned with their inability to measure differences in patients that might affect death rates. Several characteristics of hospital care were found to be associated with lower inpatient mortality: communication among and commitment of staff, clinical experience and performing operations frequently, board certification, size, and teaching status. The authors urge caution in applying the literature's findings to evaluations of hospital quality and offer suggestions for researchers. Improved research is critically important in facilitating current policy discussions regarding the use of mortality as a measure of hospital quality.