Preventing readmissions is a cornerstone of patient safety efforts. However, one concern about nonpayment for readmissions is that many may not be preventable. To determine whether they were preventable, this observational study investigated readmissions through patient and physician surveys along with chart review. Researchers determined that only one quarter of readmissions were preventable. Factors associated with potential preventability were premature hospital discharge, insufficient communication with outpatient providers, failure to discuss care goals, and emergency department decisions to readmit a patient who did not require a second inpatient stay. These results suggest that multiple interventions will be needed to avert readmissions, and such efforts will have limited impact since most readmissions are not preventable.