This case control study evaluated 250 cases and unmatched controls in discovering an association between unscheduled return visits and errors in prognosis, treatment, or follow-up care and accompanying information. Investigators analyzed numerous patient, process, and outcome measures to determine which errors were most closely associated with the identified errors. The authors focus on existing statistical relationships between unscheduled return visits and prognostic errors, poor follow-up destination with diagnostic errors, and patient dissatisfaction with information errors. While some of these findings generate natural opportunities for interventions (eg, communication between patients and providers at time of discharge from an emergency department), others require further evaluation, including identifying patients most likely to return to an emergency department based on factors such as age or chief complaint.