In contrast to traditional CPCs, in which the discussant focuses on diagnosing the disease based on the patient's presenting symptoms, the focus in Quality Grand Rounds is on diagnosing the systems problems that led to a serious error or adverse outcome for the patient. Our discussants, who are national experts in the relevant patient safety and quality issues, help the reader understand the cause of the errors, frame them in the context of what we know about patient safety, and suggest ways of decreasing the risk to future patients of similar errors. Throughout the series, discussants emphasize not only individual errors but also system failings that allowed the inevitable human fallibility to reach the patient and cause harm (13–15). For example, in this issue's “The Wrong Patient,” Drs. Chassin and Becher describe the 17 errors that came together to allow one patient to receive an invasive procedure intended for another (16). Although neither the authors nor the other discussants in the series deny or sugarcoat the individual errors, they identify the failure or absence of systems to catch patient misidentifications and a cultural milieu that provides rich soil for system problems and individual mishaps to blossom into errors. Throughout the series, readers will be introduced to patient safety concepts, such as systems thinking, the “culture of safety,” root-cause analysis, and human-factors engineering, as well as to controversies in the field, including the central question, “What is an error?”.