Recently, a change in anticoagulation therapy occurred that is still partially ignored by the healthcare community. Understanding the controversy over the use of the internal normalized ratio in monitoring patients receiving warfarin therapy is important for nurses who provide care to these patients. Five questions related to current monitoring of patients treated with anticoagulants are addressed. Nurses must recognize the importance to their practice of changes in laboratory methods and move toward using the most useful measures available to influence patients' outcomes. The international normalized ratio is the most appropriate way to evaluate the effects of warfarin therapy. All healthcare providers should use this ratio as the standard in evaluating the effects of anticoagulation therapy.