Fructooligosaccharides (FOS) have been shown to stimulate the absorption of several minerals in the intestine. In the present study, the effects of FOS on osteopenia induced by total gastrectomy were examined. Twenty eight male Sprague Dawley rats were divided into 2 groups: sham-operated (SH) and gastrectomized (GX). After a one-week adaptation period following surgery, the rats were fed synthetic diets with or without 7.5% FOS for 5 weeks. The right femur was then examined by soft X-ray, and the bone mineral density (BMD) was measured. Based on the soft X-ray findings, both cancellous and cortical bone were markedly decreased in GX rats, but not in GX + FOS rats. GX rats showed a 30% lower BMD in the metaphysis and a 20% lower BMD in the diaphysis, compared with SH rats (P < 0.01). As assessed by morphometry, significant decreases were observed in cortical bone in the diaphysis and trabecular bone in the distal metaphysis (P < 0.01). On the other hand, dietary FOS completely prevented these changes following gastrectomy. These findings indicate that dietary FOS might contribute to the prevention of bone diseases following gastrectomy.