Abstract Ultimate compressive strength was studied at mid-length of the femur of female rats centrifuged from the age of 30 days at either 2.76 or 4.15 g for 810 days. The correlation between strength and age, cuberoot of body mass, femoral length, cross-sectional area/π, outer and inner radius at femoral mid-length and γ-ray absorption is significant and positive in the control animals ranging from 30 to 840 days. Except for the correlation between strength and photon absorption, the same correlations are negative or negligible in the 2.76 g group. Analysis of covariance reveals these correlation differences to be significant as regards femoral length and inner radius. The ultimate compressive strength of bone at the femoral mid-length is 10% greater in the animals centrifuged at 2.76 g , as compared to all control animals, if the mean values are adjusted with respect to body mass and outer radius, respectively.