This paper reviews the reliability and validity of the Minimum Data Set (MDS) assessment, which is being used increasingly in Canadian nursing homes and continuing care facilities. The central issues that surround the development and implementation of a standardized assessment such as the MDS are presented, including implications for health care managers in how to approach data quality concerns. With other sectors such as home care and inpatient psychiatry using MDS for national reporting, these issues have importance in and beyond residential care management.