Current guidelines recommend the use of warfarin in all patients with atrial fibrillation (AF) and/or an artificial heart valve who are at high risk of thromboembolism. While anticoagulation with warfarin greatly reduces this risk, a careful system of monitoring and management is necessary to maintain a therapeutic dose and minimize adverse events. This rigorous process places a burden on providers, and many patients managed in typical office practices are not optimally anticoagulated.To improve the quality and efficiency of anticoagulation and remove its burden from office-based physicians, newer treatment models have evolved, including anticoagulation clinics and self-monitoring by patients at home. While these newer models often incorporate innovative programs to streamline warfarin management, little is known about their individual or relative economic merits or those of traditional office-based care. The routine costs of anticoagulation within any model have not been well documented. The cost of warfarin is readily available; however, attendant expenses, such as dose adjustment, laboratory testing, and medical encounters, are difficult to gauge. Because of these challenges in collecting practice data, most estimates of the cost of anticoagulation services have relied upon assumptions about practice patterns. Assessing the cost of anticoagulation is easier in a clinic setting because all costs relate exclusively to anticoagulation. A recent study of anticoagulation clinics estimated that annual direct costs per patient for anticoagulation services totaled approximately $US280–$US380 (2002 values). Bleeding and other complications experienced by anticoagulated patients add additional types of costs, with inpatient care accounting for more than one-half of the total cost of managing excessive anticoagulation. When quality of life is considered alongside costs to gauge the cost effectiveness of warfarin therapy versus aspirin (acetylsalicylic acid), warfarin appears to be cost-saving in patients at high stroke risk and cost effective in those at moderate risk. For patients at lower risk of stroke, aspirin is more cost effective than warfarin.With the aging of the population and consequent increases in patient groups requiring anticoagulation, the US healthcare system greatly needs improvements to anticoagulation management. New research must determine which models of management will provide the most favorable outcomes for high-risk patients at the lowest cost to payors and society.