The effects of brewer's yeast cell walls and two of its components, glucan and mannan, on the absorption of 59Fe by anemic rats were investigated. After administration of the label, the percentage of 59Fe taken up into the blood of group given glucan was generally similar to that of a group given yeast cell walls, both values were higher than in controls. The incorporation of 59Fe into the small intestines was higher in the group given glucan than in the controls or a group given a glucan-mannan mixture. Glucan is the main substance in yeast cell walls that increases iron absorption.