The authors, using the experimental pattern of bone rarefaction induced by a low calcium diet, tried to determine if 25-hydroxycholecalciferol, administered at doses and according to procedures similar to those used in osteoporosis, might interfere in such a process of rarefaction. The statistical evaluation of the results concerning the size of the amount of spongy bone presented evidence for the sharp decrease in the specific bone volume in rats placed on a low calcium diet as compared to control rats. Such a difference is found even between rats treated with 25-OH-D3. Nonetheless, the authors reported a difference--although not statistically significant--that indicated an increase in the amount of bone in rats on a normal diet but treated with vitamin D as compared to control rats.25-OH-D3 by itself, the diet being the same, was not able to ameliorate the amount of bone.