Hospital quality scores are publicly available, but the extent to which they reflect patient safety remains controversial. This study compared measures from the Leapfrog Group, which incorporates mandatory publicly reported data and voluntary self-reported data to give each hospital a letter grade, to mandatory publicly reported data on the Medicare's Hospital Compare website. Investigators found that most Leapfrog voluntary scores were close to perfect. For hospitals that did not report the voluntary component of the Leapfrog score, they modeled how the hospitals' overall letter grades would change if they had self-reported different performance levels. They found that self-reported data heavily influenced a hospital's letter grade. Leapfrog scores were not consistently associated with Hospital Compare data on hospital-acquired conditions like health care–associated infections, pressure ulcers, or falls. The authors suggest that Leapfrog data provides only a limited assessment of hospital performance.