High pressure treatment was applied to extra virgin olive oils and to seed oils in order to verify if and to what extent modifications in the lipidic fraction can occur. Six different extra virgin olive oils and five different seed oils (grape-stone, sunflower, soybean, peanut, maize) were treated at 700 MPa for 10 minutes at room temperature. Different analytical parameters (peroxide value, para-anisidine value, rancimat test, volatile hydrocarbons) were measured to study the oxidative stability of the treated oils. The application of high pressure at these operating conditions produced changes in the p-anisidine values, but not in the peroxide values and volatile hydrocarbons of the oil samples. As expected, in all cases, the olive oils were more resistant to oxidation than the seed oil samples. It is necessary to point out that the effects of high pressure treatment on oils depend on their origin, composition, initial quality and age.