OBJECTIVES: Although the fracture risk assessment tool (FRAX) developed by WHO is considered to be valid and reliable, its algorithm is not open to the public and is thus unavailable for economic evaluations. The purpose of this study was to develop a state transition model with risk equations for osteoporotic fracture in Japanese women and to verify the validity of our model by comparison of the predicted 10-year osteoporotic fracture probabilities in our model and those derived from the FRAX. METHODS: Equations for age and femoral neck BMD specific incidence of hip, clinical spine, and other fracture were developed using a series of methods by De Laet, et al and epidemiological data of postmenopausal Japanese women. A patient-level state transition model with ten health states using the equations was used to predict the 10-year probability of a hip fracture and a major osteoporotic fracture in Japanese women with osteoporosis, who had no treatments.  We ran the model with different combinations of BMD (T-score－1.5, －2.0, or -2.5), and the number of clinical risk factors (0, 1, 2, or 3). The predicted values in our model were compared with those of the FRAX. RESULTS: For 70-year-old women with different combinations of T-scores and the number of clinical risk factors, the estimated 10-year probabilities of hip fracture in our model were almost identical to those of the FRAX. The 10-year probabilities of major osteoporotic fracture in our model also appeared to be consistent with those of the FRAX. These findings supported the validity of our model in the use of health economic evaluation.  CONCLUSIONS: The developed model appears to be a valid model for use in economic evaluation in osteoporosis from the perspective of Japan healthcare system. The relation between 10-year fracture probability and ICER of osteoporosis treatment can be estimated using this model.