This AHRQ-funded case-control study used physicians' clinical judgment about flagged complications to generate potential deficiencies in the quality of care. Compiling data for more than 1000 Medicare beneficiaries from acute-care hospitals, investigators captured cases with a documented surgical or medical complication along with matched controls without such complications. The authors report that potential quality problems were identified at much higher rates in the flagged cases, but the judgments made about quality were affected by many circumstances, such as the complexity of a given case. Therefore, while subjectivity in physician case review exists, this study offers a potential strategy for selecting cases that might increase the yield in such interpretations of quality.