AIM: To investigate the skeletal effects of total tanshinone in ovariectomized rats by analyzing cancellous bone histomorphometry of fourth lumbar vertebrae (LV4) and proximal tibial metaphyses (PTM). METHODS: Fourmonth-old Sprague-Dawley female rats were sham-operated and treated with vehicle or ovariectomized and treated with either vehicle, total tanshinone (200 mg.kg-1.d-1, equivalent to 35 μg.kg-1.d-1 of tanshinone II A and 16 mg.kg-1.d-1 of gery for 10 weeks. Double in vivo fiuorochrome labeling was administered to all rats. The undecalcified longitudinal LV4 and PTM sections were cut and stained with Goldner’s Trichrome (4-μm thickness) or unstained (8-μm thickness) for the bone histomorphometric analysis. RESULTS: A significant decrease in trabecular bone volume (BV/TV) and trabecular number (Tb.N) and a significant increase in osteoclast surface (OCS/BS) and mineralizing surface (MS/BS) were found in both LV and PTM of vehicle-treated OVX rats compared with sham controls.Tanshinone completely prevented the decreases in BV/TV and Tb.N and the increase in OCS/BS in the LV4, and partially prevented the decreases in BV/TV and Tb.N in the PTM of OVX rats. In addition, tanshinone increased trabecular thickness (Tb.Th) whereas it did not alter MS/BS. Moreover, tanshinone had no effect on uterine weight and body weight of OVX rats. Estrogen treatment increased BV/TV and Tb.N and decreased OCS/BS, but, also markedly decreased MS/BS and increased uterine weight in OVX rats. CONCLUSION: The current study demonstrated that the adequate supply of tanshinone prevented OVX-induced cancellous bone loss in rats through inhibition of elevated bone resorption.