The selection of suitable markers from the secondary metabolism of lipoxygenase, in experimental olive oils produced from drupes harvested in different areas of the Italian Calabria region and of Tunisia, allows an easy discrimination between each cluster of samples. The origin of the foodstuff can be ascertained even when the distances between the production zones are very close to each other as in Calabria. Olive oils produced from irrigated and nonirrigated farms in Tunisia were also clearly distinguishable. The markers were detected by chemical ionization mass spectrometry with an ion trap gas chromatography-mass spectrometry apparatus. The quantitative data of Calabrian olive oil samples were subjected to linear discriminant analysis, whereas the Tunisian data were treated by means of other two statistical tools, i.e., the Kruskal-Wallis test and the Wald-Wolfowitz test.