Nearly all patients will experience a diagnostic error in their lifetime, sometimes with devastating consequences. That conclusion by the Institute of Medicine (IOM) of the National Academies of Sciences, Engineering, and Medicine in a recently released report, “Improving Diagnosis in Health Care,” should mobilize collaboration among patients, health care professionals and organizations, government, and the private sector to improve the diagnostic process.1 Diagnostic errors have received less attention than other medical errors, even though correct diagnosis is fundamental to subsequent choices. Diagnostic errors occur in every health care setting and clinical area.