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Introduction: Clinical decision rules have been designed and developed to assist physicians in identifying the patient with osteoporosis. The aim of this study was to evaluate the performance of three decision rules in an Iranian post menopausal population. Materials and Methods: Three osteoporosis risk indices, the osteoporosis self assessment tool (OST), osteoporosis risk assessment instrument (ORAI), and the body weight criterion for 5573 out patients without any risk factors for secondary osteoporosis or receiving active bone medication and with negative history of prior fragility fraction were calculated. BMD at spines and femoral neck were measured via dual x-ray absorptiomety and the patients categorized to normal, osteopenic and osteoporotic according to WHO criteria. The sensivity, specifity, positive predictive value negative, predication value and area under receiver operating curve in identifying the osteoporotic women were determined for each decision rule and compared. Results: In this study, the prevalence of osteoporosis was 30.8%, 20% in lumbar spines and neck of femur, respectively. The sensivity of these risk indices in indentifying women with osteoporosis ranged from 70% to 84/1% and the specificity ranged from 44.6-65.6%. The area under curve (ROC) in identifying those patients with osteoporosis was significantly better for OST (0.75) and ORAI (0.74) compared with the body weight criteria (0.66). The negative predicative value ranged from 80% to 93%, while positive predication values ranged from 33% to 54%. Conclusion: Our data provide evidence showing OST, ORAI to be useful clinical tools, assisting clinicians in making decisions regarding which women need to be to referred for BMD testing but more evidence however needed is to confirm validity of body weight criterion.