The purpose of present trial is to investigate the effect of exercise therapy on osteoporosis. 90 postmenopausal osteoporotic women referred to the physical medicine and rehabilitation clinic are randomized into three groups of 30 people. Then, drug therapy; including alendronate, calcium, and vitamin D is begun in all three groups. In the second and third groups, different exercises are also applied in addition to medication. In the second group, aerobic exercise, including walking on the treadmill and stationary cycling, and in the third group isotonic and isometric strengthening exercises of trunk and hip and knee muscles, are conducted for 9 months with three months relative resting phase.In other words our sports therapy program was over ally included six month exercise accompany with three month home-based exercises within therapy periods. Before treatment, quadriceps muscles strength, hip abductors and extensors of trunk are determined by MMT. To measure the balance status, fall risk and postural stability indices are determined using Biodex balance training instrument. Bone density of lumbar and femoral neck areas are measured by DEXA method and T-score is determined. Finally, SF36 questionnaire of "quality of life" is completed by the patients. The above-mentioned check-ups will be repeated and compared again after 6 months in all three groups