The emergency department is considered a high-risk setting for diagnostic errors. This analysis of Medicare claims data found that a significant number of adults age 65–89 died within a week of visiting and being discharged from an emergency department, even when no life-limiting illness was noted. Hospitals that admit a lower proportion of emergency department patients to the inpatient setting had a higher mortality rate among discharged patients, even after adjusting for patient characteristics. Consistent with prior studies relating patient outcomes to volume, higher-volume emergency departments had lower 7-day mortality among discharged patients. These results suggest that emergency department discharges may represent missed diagnoses. A WebM&M commentary discussed an incident involving a patient who died after being discharged from the emergency department.