The solubilities and activity coefficients of six chlorinated organic compounds were determined in aqueous electrolyte solutions by UV-vis spectrophotometry at 25-degrees-C. The salting-in and salting-out constants were determined. The systems studied were chlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, and 1,2,4-trichlorobenzene in solutions of NaCl, KCl, Na2CO3, K2SO4, and CaCl2, chlorobenzene in solutions of (C2H5)4NBr, and 2,4-dichlorophenol and 2,4,6-trichlorophenol in solutions of NaCl. The experimental values were compared with those calculated from five salt effect theories. The modified internal pressure theory gives the most satisfactory results.