OBJECTIVE: To evaluate the cost-consequences of LMWH compared with unfractionated heparin in the treatment of unstable angina pectoris in Japan. METHODS: A cost-consequence analysis was performed using decision-analytic modeling using evidence from the FRISC (Fragmin during Instability in Coronary Artery Disease) study group, Sweden. The decision tree models a patient presenting with unstable angina pectoris and facing the alternative treatments: LMWH or heparin as a basic model. Also, an advanced model was constructed with treatment options that reflected more realistic practice patterns in Japan. Cardiologists reviewed the model-development process to make the model relevant to the Japanese medical environment. The direct costs were obtained from pilot studies of DRGs in Japanese national hospitals. RESULTS: In the basic model, we estimated a slight difference of expected costs between LMWH and heparin, favoring LMWH. However, this model was limited in two main areas: 1) difference in effects between LMHW and heparin were not statistically significant in the FRISC study; 2) opportunity costs such as monitoring for heparinization and treatment of bleeding with heparin were not included. When we incorporated realistic assumptions regarding the opportunity costs and Japan’s treatment patterns, we found that total medical costs for the LMWH group were much lower than the heparin group even if the clinical effects for heparin and LMWH were set as equal. In this case, the estimated cost in the LMWH group was about $11,300 per patient, and $19,600 for the heparin group assuming LMWH is properly used in clinical practice. This result was robust to a range of sensitivity analyses. CONCLUSION: The use of LMWH for unstable angina pectoris in actual clinical practice where heparin monitoring can be avoided appears to be cost-saving in Japan. Considering the target population of 700,000 patients in Japan, the LMWH will have a great economic impact on the society.