Selective solubilization of o-/p-chlorobenzoic acids and o-/p-nitroanilines has been attempted using aqueous solutions of sodium butyl monoglycol sulfate as the hydrotrope. An association model is proposed to fit the solubility data of these isomers and to characterize the hydrotrope-hydrotrope and hydrotrope-solute interactions. The solubility of an o-isomer in the aqueous hydrotrope solutions is higher than the solubility of the corresponding p-isomer, and thus the o-isomer can be selectively solubilized. The solubility of nitroanilines remains unaffected in the presence of the other isomer while chlorobenzoic acids modify the solubility of each other. Thus the separation is affected by the composition of the mixture as well as by the concentration of the hydrotrope. The solubilized material can be recovered by dilution with wafer.