Missed diagnostic opportunities often involve multiple process breakdowns and can lead to serious avoidable patient harm. Based on a web-based survey of 1,594 emergency medicine physicians, missed diagnostic opportunities most frequently occur in children who present to the emergency department with undifferentiated symptoms (e.g., abdominal pain, fever, vomiting) and often involve issues related to the patient/parent-provider interaction, such as misinterpreting patient history or inadequate physical exam.