Quaternary ammonium salts, among them Aliquat 336, are known to be efficient extractants of many solutes, such as anionic species (Cl-, Br-, CrO42-, ...), mineral acids, organic acids, enzymes, and hormones. However, due to the complex behavior of liquid-liquid systems implying this type of extractants, different approaches have been tried in the literature to find a suitable mathematical model able to predict equilibrium experimental data. In this work, taking into account the difficulty previously reported, the liquid-liquid equilibrium system NaOH-chloride of Aliquat 336 in kerosene has been experimentally studied in the range of concentrations of 0.25 M less-than-or-equal-to C(OH-) less-than-or-equal-to 2.0 M and 1% v/v less-than-or-equal-to C(Aliquat 336) less-than-or-equal-to 10% v/v. The mathematical model developed under the consideration of a nonideal behavior of both liquid phases and including two fitting parameters satisfactorily predicted the experimental data.