Objective:To evaluate the clinical efficacy of ibandronate and alendronate in postmenopausal osteoporotic women. Methods:A total of 32 postmenopausal women with osteoporosis were randomly classified into two groups,16 in each:group A,oral ibandronate 150 mg per month;and group B,oral alendronate 70 mg per week. All patients received calcium 500 mg and Vitamin D 200 IU daily for one year. All patients were examined by DEXA(lumbar,hip)before and after treatment. At the same time the biochemical marker of bone resorption serum C-terminal telopeptide-I(CTX-1)was determined. Results:The BMD of lumbar spine(L2-4)significantly increased compared with that of pretreatment in both groups(P < 0.05),the BMD of hip locations also increased but without significance. The increases of BMD in ibandronate group were 15.34%,4.15%,5.05%,2.49% at L2-4,femoral neck,trochanter and the total of hip respectively,those in alendronate group were 14.50%,4.42%,1.18%,2.64% respectively; serum CTX-1 levels decreased dramatically in both groups(P < 0.05). The BMD change rates in all locations and the CTX-1 decreases at all time points between the two groups were not significant. Conclusion:Ibandronate is more convenient for long-term use than alendronate,which is as effective as alendronate for increasing bone mineral density and for inhibiting osteoclastic activity in treatment of postmenopausal osteoporosis.