Effects of ingestion of breakfast cereal containing wheat bran on both the fecal properties and the frequency and the feeling of defecation were investigated in 46 adolescent Japanese females. The subjects were devided into constipating and non-constipating groups and were given wheat bran cereal (WB) or placebo cereal (P) for a week in a cross-over manner. WB contained 5.64 g of dietary fiber per daily intake (40 g). Although the fecal volume and the frequency of defecation of the constipating group were significantly lower than those of non-constipating group, no significant difference in nutrient intake was observed between the groups under their ordinary conditions. Overall data indicated the existance of an inclination to constipation due to deficiency in dietary fiber in Japanese young females. However, the dietary fiber intake was significantly increased by taking WB(p<0.05). The frequency of defecation in both groups and the fecal volume in constipating group during the period of WB ingestion were significantly higher than those during the period of P ingestion (p<0.05). These results showed that the ingestion of WB effectively supplemented dietary fiber and improved defecation of adolescent females with a tendency to constipate.