Immature male Wistar rats were given a zinc-depleted semi-synthetic diet (2 mg Zn/kg diet) for 4 weeks. Control groups received a similar diet containing 60 mg Zn/kg diet, either ad lib. or in amounts matched to the consumption of the Zn-deficient group. Rates of growth and food conversion efficiency were markedly lower in the Zn-deficient group compared to controls. The phloridzin-sensitive uptake of galactose and 3-O-methyl glucose by everted jejunal rings from each group was measured over a range of concentrations. Kinetic analysis revealed that the maximum transport rate (Vmax) for the uptake of both sugars was significantly higher in the Zn-deficient group than in the control groups. The villi, microdissected from samples of proximal jejunum, were significantly shorter and narrower across the base in the Zn-deficient group than those of the control groups, but were present in greater numbers per unit serosal area. The present study shows that Zn deficiency leads to significant morphological changes in rat small intestine, which are accompanied by an increase in the capacity of the tissue to take up sugars across the mucosal membrane.