In the evaluation of the oxidative stability of the vegetable oils with the addition of additives, it was noticed that the antioxidant TBHQ showed a small antioxidant effect in the sunflower and soybean oils, in the two concentrations investigated. In relation to corn oil, it displayed a prooxidant action, reducing the OIT values in the range from 34.2 to 33.1 %, as compared TCO100 and TCO200 samples, respectively. It should be stressed that 200 mg kg-1 is the highest concentration of TBHQ allowed by the Brazilian legislation. This result, however, does not indicate that TBHQ is an antioxidant that cannot be applied to corn oil; it only indicates that the experimental conditions of pressure and temperature, in the present study, were not adequate for the evaluation of the antioxidant efficiency of TBHQ to corn oil.