There are many factors will influence the dosage of warfarin and the INR level (e.g. liver and renal function, disease status, nutritional status, and drug-drug interaction). The effectiveness of pharmacist anti-coagulation clinic has been approved that can improve the efficacy and the safety of using warfarin. The pharmacist anticoagulation clinic in National Taiwan University Hospital has been established since 2012. This article will share the execution of pharmacist anti-coagulation clinic.