Gastrectomy-evoked osteopenia in the femoral metaphysis of rats can be prevented by the consumption of fructooligosaccharides (FOS). We examined the effect of FOS on the femoral neck. Twenty-eight 5-week-old male Sprague-Dawley rats were divided into two groups, sham-operated (SH) and gastrectomized (GX). One week after each operation, the rats were fed diets containing 0.5% calcium with or without 7.5% FOS for 4 weeks. After dietary treatment, the middle of the femoral neck was cross sectioned. Backscattered electron images of the sections were then taken to calculate the following morphometric parameters: (1) percent trabecular bone volume (%TBV), (2) percent cortical bone volume (%CBV), and (3) percent bone marrow cavity (%MV); all were determined relative to the entire scan area (SC). Calcium, phosphorus, and magnesium (weight percent) were then measured on the cortical bone by energy-dispersive X-ray analysis. Total bone volume (%BV = %TBV + %CBV) and %CBV were almost identical among the groups, except in GX rats. In GX rats, these variables were significantly (approximately 20% and 30%, respectively; P < 0.01) less than those in SH rats, whereas there were no changes in the other groups over the entire scan area. The calcium concentration close to the periosteal surface of cortical bone was markedly reduced by gastrectomy. This reduction was completely prevented by FOS consumption. These results suggest that FOS consumption prevents gastrectomy-evoked osteopenia regarding both volume and calcium concentration of the femoral neck.