Objective:To study the effect of rosiglitazone on the bone microarchitecture of bilaterally ovariectomized(OVX) rats. Methods: Twenty-one 24-week-old skeletally mature rats were bilaterally ovariectomized,and were randomly divided into three groups (n=7):Control group(C group),Rosiglitazone A group(RA group),and Rosiglitazone B group (RB group). Rats in RA group were given i.g 0.35 mg/d rosiglitazone for four weeks and those in the RB group were given i.g 0.70 mg/d rosiglitazone. Rats in the control group were given normal saline in the same manner. The rats were sacrificed four weeks later. The bone volume/tissue volume(BV/TV),the trabecular number(Tb.N),the trabecular thickness(Tb.Th),the trabecular separation(Th.Sp),and the bone surface/bone volume(BS/BV)of the femur,tibia,and lumbar were determined by micro-computered tomography(micro-CT). Results: Compared with the control group,the Tb.N,Tb.Th,and BS/BV of the femur,tibia,and lumbar all decreased significantly in RA group (except for the BS/BV of tibia) (P<0.05,P<0.01); the Tb.SP of tibia and lumbar in the RA group were significantly increased (P<0.05); and there were no differences in BV/TV between the two groups. Compared with control group,the Tb.N,Tb.Th,and BS/BV of the femur,tibia,and lumbar were decreased significantly in RB group(P<0.05,P<0.01); the Tb.Sp of tibia and lumbar increased significantly(P<0.05); and the BV/TV had no differences between the two groups. There were no significant differences between the RA group and RB group concerning all the parameters. Conclusion: Rosiglitazone can cause injury to the bone microarchitecture,especially to the cancellous part of the bone.