This paper presents the correlative changes of cancellous bone histomorphometry, biomechanical property and bone mineral contents of lumbar vertebrae in ovariectomized rats. Forty eight 10.5-month-old female SD rats were randomized to six groups: 1) Basal: at 10.5 mon. of age; 2) sham-1: sham-operated at 13 mon. of age; 3) OVX-1: ovariectomized at 13 mon. of age; 4) sham-2: sham-operated at 16 mon. of age; 5) OVX-2: ovariectomized at 16 mon. of age; and 6) OVX-2 + EE: ovariectomized and treated with 17 alpha-ethynylestradiol (100 micrograms.kg-1.d-1) starting at 13 mon. of age for 12 weeks. Double in vivo fluorochrome labeling was administered to all rats. At the end-point of study, the undecalcified longitudinal fourth lumbar vertebra (LV4) sections were cut and stained with Goldner's Trichrome for bone histomorphometric analyses. The mechanical properties of the compact fifth lumbar vertebra body (LV5) were measured with compression test, the LV5 bodies then were dried constantly with high temperature and digested with acid for testing of bone mineral content. A trend in trabecular bone volume (BV/TV), trabecular thickness (Tb.Th) of LV4, bone break load, break stress, elastic moduli and bone calcium content of LV5 to increase with the increase of age was revealed in the intact rats, but the highest value was at 13 mon. of age. A positive correlation was seen between histomophormetry and bone bio-mechanical properties in the intact rats. Compared with the data from the sham-operated rats, the BV/TV and Tb. Th significantly decreased and bone turnover rate significantly increased in OVX rats at 10 weeks, and the above parameters further decreased 22 weeks post OVX. Correspondingly, the bone break load, break stress, elastic moduli and bone calcium content significantly decreased with the increase of time post OVX was compared with those of sham-operated rats. A positive correlation between histomophormetry and bone biomechanical properties was also observed in OVX rats (r = 0.399, P = 0.018). Bone histomorphometry is good for predicting early physiological and pathological changes and bone biomechanical properties are good parameters for predicting corresponding function of bone such as fracture. Both of them are useful and needful in the animal studies on osteoporosis and related pharmacodynamic observations on new drugs.