Two mixed bed ion-exchange resins (Dowex Monosphere MR-450 UPW and Amberlite MB-150) were investigated for their ability to remove oleic acid from a laboratory-prepared 5 % (w/w) oleic acid/soybean oil mixture. The performance of the heterogeneous mixed-bed resins to remove oleic acid from the mixture was investigated for resin loading and reaction duration while the mixing rate, reaction temperature, and initial oleic acid composition of the mixture were kept constant. Both resins removed > 93 % of the oleic acid in the sample within 4 h with a 20 % (w/w) resin loading in a nonpressurized batch reactor system at 50 degrees C. The maximum adsorption capacity for Amberlite MB-150 and Dowex Monosphere MR-450 UPW was determined to be 0.27 g.g(-1) (oleic acid/wet resin) and 0.26 g.g(-1) (oleic acid/wet resin), respectively. Ion-exchange of oleic acid onto the quaternary ammonium site of the mixed-bed resin was determined to be the mechanism of oleic acid removal. The presented research has promising application in the areas of refining edible oils and biodiesel production from free fatty acid-containing feed stocks.