The objective of the studies was to determine oxidative changes in the stored olive oils. The analysis was based on the changes in peroxide values and the changes in fatty acid composition. Kinetic analysis methods were used to work out the results. After 5 weeks storage at 21°C in the dark a significant increase in the value of peroxide value (11.6–15.3 mEqO₂/kg) occurred in the case of raw olive oils. All these olive oils are unsuitable for consumption. For other samples with refined olive oil added, the peroxide values are 3.6 – 7.6 mEqO₂/kg. The calculated values of the time of attaining the critical value of PV are very differentiated (5.3-9.5 week). All the studied fat oxidation processes were of aw type, of the rate rising in time. They are characterised by various dynamics. It is confirmed by diverse process orders varying from 1.6 aw to 6.6 aw. It was found that the initial peroxide value does not decidedly affected the auto-oxidation process course nor on the time of reaching of critical value. Pressed olive oils proved to be more stable (n=1.6 aw and n=2.4 aw). After 5 weeks storage a minor decrease in the UFA content and a small increase in the SFA content occurred. Olive oil did not contain trans fatty acids.