OBJECTIVES: Two models of ambulatory oral anticoagulation management have been adopted in a teaching hospital in Hong Kong, namely the anticoagulation clinic (AC) and routine medical care (RMC). The objective of this study was to compare the cost and outcomes of warfarin therapy management at AC and RMC from the perspective of a public health organization. METHODS: A retrospective observational study was performed by reviewing the medical records of outpatients who were initiated on warfarin from January 1, 1999 to June 30, 2001 in a teaching hospital. Effectiveness was assessed by percentage of patient-time spent in target INR range and the incidence of thromboembolic events (TE). Safety was assessed by incidence of hemorrhage and warfarin overdose (INR>5). Direct medical cost associated with the management of warfarin therapy and anticoagulation complications was also evaluated. The incidences were expressed as percentage per patient-year. RESULTS: Forty-one patients (71 patient-years) and 476 patients (409 patient-years) were started on warfarin in AC and RMC, respectively, during the study period. Patients managed by AC spent significantly more time in target INR range than those in RMC group (58 % vs. 44%; p=0.002) and had a lower incidence of INR>5 (1.4% vs. 7.1%; p=0.068). The AC group patients had a lower rate of TE (4.2% vs. 7.6%; p=0.443) and major to fatal bleeding (0% vs. 9.5%; p=0.01). The total direct medical cost of AC was lower than that of RMC by 44% (HKD4838 vs. HKD8595 per patient year; 1USD=7.8HKD). CONCLUSION: The establishment of the AC improved the effectiveness, safety, and decreased the direct medical cost of oral anticoagulation therapy.