The landmark 1999 Institute of Medicine report, “To Err Is Human,” challenged us all to reduce the number of preventable medical errors. While vulnerabilities and patient harm continue at unacceptable rates, there are also many success stories. This article presents a series of case studies that illustrate how healthcare organizations have used data—quantitative, qualitative, and comparative—to address vulnerabilities and guide meaningful change to improve patient safety. These examples are drawn from the data-sharing community of CRICO Strategies, a division of the Risk Management Foundation of the Harvard Medical Institutions, Inc. (CRICO). CRICO's data-driven strategy uses intelligence from thousands of medical malpractice cases across the country to examine what has gone wrong and why, and to help members and clients manage their risk and provide better care.