We experimentally evaluated the effects of multicomponent systems of divalent cations on the performance of mixed-bed ion exchange in the concentration range used for ultrapure water processing. Data were collected in the batch and continuous column systems with Dowex Monosphere resins used commercially for ultrapure water applications. The presence of divalent cations in the systems affects significantly the capacity of the units to remove a univalent cation. However, the anion exchange rate increases slightly in the multicomponent systems. The equilibrium and the breakthrough curves of ions, plotted as the ratio of the effluent to influent concentration versus run time or solution volume passed through the experimental column, give detailed results about the effects of the existence of other ionic species on the fate of each ion in MBIE units. The results of the present study are expected to be used to develop and simulate mathematical models and to understand the performance of mixed-bed ion exchange at ultralow concentrations.