The removal of Cr(III) in an aqueous solution by an alkaline solution was experimentally and theoretically investigated. The experiment was carried out in a batch stirred reactor at room temperature. A mathematical model based on mass and charge balances of reactions in the solution at an equilibrium condition was proposed. The effects of certain parameters, such as pH, initial Cr(III) concentration in the solution, and the ratio of NaOH/Ca(OH)(2) added to the solution, were investigated. The removal increased with pH and initial Cr(III) concentration. The use of the NaOH/Ca(OH)(2) ratio was the most important variable affecting the removal. The results show that Cr(III) removal about 100% in the solution was achieved when the solution was treated at pH 6.8 under the current experimental condition. It was also shown that the results thus obtained using the model is in good agreement with experimental data.