The ultimate goal of warfarin therapy, to prevent thromboembolism with the lowest possible risk of major bleeding complications, is most likely to be realized when therapeutic anticoagulation as measured by the international normalized ratio (INR) is quickly achieved and maintained in appropriate candidates. Realizing this goal requires optimal functioning of various anticoagulation management system components. The extent to which these components function smoothly together determines the quality of warfarin therapy management. A quality measure is used to ascertain the degree to which a given system is successfully coordinating care to accomplish a particular therapeutic goal. The quality of care can be evaluated at different levels such as outcomes (e.g. INR results, major bleeding, thromboembolism, death), processes (e.g. method used to adjust warfarin doses), and structures (e.g. clinic organization structure, workload statistics). There is great need for a structured program of quality measurement for warfarin therapy management. The arrival of new options for oral anticoagulation medications increases the need for credible information regarding the site-specific quality of warfarin therapy management because the potential advantages over warfarin therapy associated with some of these agents are in part dependent upon the quality of warfarin therapy management.