Health care practitioners and change experts contend that organizational readiness for change is a critical precursor to successful change implementation. This article assesses how organizational readiness for change has been defined and measured in health services research and other fields. Analysis of 106 peer-reviewed articles reveals conceptual ambiguities and disagreements in current thinking and writing about organizational readiness for change. Inspection of 43 instruments for measuring organizational readiness for change reveals limited evidence of reliability or validity for most publicly available measures. Several conceptual and methodological issues that need to be addressed to generate knowledge useful for practice are identified and discussed.