To describe the background, history, and approach of the OECD Health Care Quality Indicators (HCQI) Project, an initiative to implement quality measures for international benchmarking of medical care at the health system level.The participating countries and international organizations selected five priority areas (cardiac care, diabetes, mental health, patient safety, and primary care/prevention) and developed a conceptual framework to guide the project. International expert panels were formed to identify clinically important, scientifically sound, and feasible measures based on a structured consensus process.The consensus process was successfully completed in all five priority areas leading to a recommendation of 86 indicators. Nine indicators were selected for diabetes, 12 for mental health, 17 for cardiac care, 21 for patient safety, and 27 for primary care and prevention.The initial experience of the HCQI Project demonstrates that international consensus can be achieved in how to measure the quality of care in priority areas, suggesting substantial demand for and interest in comparative information at the health system level. However, much additional work remains necessary before the project can supply policymakers and researchers with ongoing, comprehensive, and reliable data on the quality of care in industrialized countries.