The Healthcare Cost and Utilization Project (HCUP) announces release of the 2015 Nationwide Readmissions Database (NRD). The NRD is an annual database designed to support various types of analyses of national readmission estimates for all payers and the uninsured. This database addresses a large gap in health care data—the lack of nationally representative information on hospital readmissions for all ages. Note: On October 1, 2015, hospital administrative data began using ICD-10-CM/PCS, so the first nine months of 2015 contain ICD-9-CM codes and the last three months contain ICD-10-CM/PCS codes.1 Data elements and data structure for the 2015 NRD have changed. Trends based on diagnoses or procedures will be affected.