The effect of cadmium on zinc absorption was studied using an isolated vascularly and luminally perfused rat intestinal preparation. 65Zn as well as Zn and Cd (both as the chloride salt) were added to the luminal perfusion medium (LPM) at varying concentrations. Over a 90-min period, the amount of Zn appearing in the vascular perfusion medium (VPM) and that retained by the tissue post-perfusion was estimated. Cd at all levels studied (0.03, 0.10, 1.0, and 10.0 micrograms/mL) reduced the amount of Zn appearing in the VPM in comparison with control perfusions (no detectable Cd in the LPM) when the initial Zn concentration was 5 micrograms/mL. Similarly, with an initial Zn concentration of 10 or 20 micrograms/mL, the amount of Zn appearing in the VPM was reduced when the Cd concentration was 0.1 or 1.0 micrograms/mL. With these same Zn concentrations, the amount of Zn retained by the tissue was higher when the Cd concentration was 10 micrograms/mL. These results demonstrate that Cd at low concentrations is capable of reducing Zn appearance in the VPM.