Smectites are the most commonly found mineral in temperate region soils. Smectites exhibit variability in shrink – swell behavior and sorption of organic molecules. Previous research has established the inter-relation between extent of swelling and sorption of organic compounds by smectites. The effect of the interlayer cation on sorption of organic compounds and the inter-relationship between cation exchange selectivity and extent of swelling has also been demonstrated. We investigated the effect of sorption of an organic compound on cation exchange selectivity and the interaction between organic-sorption, cation exchange and clay swelling. Our hypothesis is that adsorption of organic molecules in the interlayers of smectites influences the affinity of the clays for inorganic cations in aqueous systems. Ca- and K- saturated SPV (Bentonite) and SAz1 were equilibrated with mixed salt solutions containing 0.01M KCl and 0.005M CaCl2 in the presence or absence of 200 ppm m-dinitro benzene. Concentrations of Ca and K in solution and on the clay were analyzed on the ICP-AES and concentrations of m-DNB were measured using a Spectrophotometer. In general, the K-saturated smectites sorbed more M-DNB than the Ca-saturated smectites and the SPV sorbed more m-DNB than the SAz. Sorption of m-DNB on SPV increased preference for K relative to Ca for samples initially saturated with Ca, but had little effect on exchange selectivity for samples that were initially saturated with K. The net effect of M-DNB was to decrease the magnitude of the hysteresis loop for the Ca-K exchange. There was little effect of M-DNB on K-Ca exchange for the SAz. Our results demonstrate that adsorption of organic molecules in the interlayers of smectites influences the affinity of the clays for inorganic cations and that hysteresis in cation exchange influences sorption of organic molecules.