Differences in structural and crystallinity between the lateral and medial regions of the central femoral diaphysis in low-mineral-diet-fed ovariectomized rats were investigated using polarization microscopy and Raman spectral analysis. Eighteen 19-week-old female Wistar rats were divided into 3 groups (Group 1: sham ovariectomy + normal diet group, Group 2: ovariectomy + normal diet group, Group 3: ovariectomy + low-mineral-diet group). Measurements were performed in the lateral and medial regions of the femoral sagittal cross-section at 24 weeks of feeding. On polarization microscopy, tubular structures of haversian and Volkmann's canals and osteocytes were observed in the femur in Groups 1 and 2. In Group 3, the number of these tubular structures in the femur was decreased compared to those in Groups 1 and 2. Moreover, the bone width of the femur decreased in Group 3 compared to those in Groups 1 and 2. On Raman spectral analysis, the peaks of organic and inorganic components were observed in the lateral and medial regions of the femur in all groups. In magnified views of the peak of v(1)PO(4)(3-) spectrum, the peaks in the lateral and medial regions overlapped in Group 1, but the peak of the medial region was about 0.3 and 0.8 cm(-1) shifted toward the low wavenumber side compared to those of the lateral region in Groups 2 and 3, respectively. Based on these findings, the influences of reduced estrogen secretion and the low-mineral diet were clarified as differences in the femoral structural and crystallinity on polarization microscopy and Raman spectral analysis. Since highly sensitive detailed point analysis can be performed within a short time using Raman spectral analysis, it may be useful for high-dimensional structural analysis.