It has been well documented that ascorbate enhances iron uptake, with a proposed mechanism based on reduction to the more absorbable ferrous form. We have performed a study on the effects of ascorbate on ferric iron uptake in the human epithelial Caco-2 cell-line. Ascorbate increased uptake in a concentration-dependent manner with a significant difference between iron uptake and reduction. Uptake kinetics are characteristic of a non-essential activator and the formation of an Fe(3+)-ascorbate complex. This investigation provides evidence that ascorbate enhances the apical uptake of ferric iron into Caco-2 cells through the formation of a Fe(3+)-ascorbate complex.