Fatty acid composition of a frying oil is very important in order to limit the reactions of oxidation, hydrolysis and polymerization which may occur during cooking operations. The objective of this study was to evaluate the thermal stability of olive oil, super palm olein and sunflower oil during frying of frozen French fries. Termo-oxidized oil, frying oil and oil extracted from potatoes were subjected to the following analysis: free fatty acids (AGL), peroxide value (NP), total polar compounds (CPT) and analysis of the methyl esters fatty acids (EMAG). In addition, each sample has been characterized by analysis of the dynamic headspace coupled to gas chromatography -mass detection (DHS / GC-MS). In thermo-oxidized olive oil 2,4-E, E-decadienal, 2,4-E, E-nonadienal and acids showed a good correlation with the CPT as well as the 2E-non-enal and n-butyl pyrrole in thermo-oxidized sunflower oil. The fat extracted from potatoes fried with palm olein was found to contain styrene which seems to arise not only from a phenomenon of migration from packaging material but from a mechanism of neo-formation. Alkylbenzenes and pyrazines were detected in the fat extracted from potatoes fried with sunflower oil and olive oil.