OBJECTIVES: This study examined the consistency of hospital mortality rates across different diagnoses. METHODS: Standardized mortality ratios for patients discharged in 1991 from US hospitals were determined via the Medicare Hospital Information Report. RESULTS: Correlations between standardized mortality ratios for different diagnoses were relatively weak, ranging from .03 to .34. Agreement between hospital rankings (based on standardized mortality ratios), as measured by the weighted kappa statistic, was also weak. CONCLUSIONS: The present results indicate that hospital mortality rates for individual diagnoses are weakly associated. Thus, it may not be valid to generalize conclusions about hospital performance from a single diagnosis.