The aim of this study was to determine the chemical composition of the essential oils of Algerian citrus. They were extracted by hydrodistillation from the leaves of citrus species (orange, Bigaradier, mandarin and lemon), using gas chromatography/mass spectrometry (GC/MS). Their chemical composition and antifungal activity against four phytopathogenic fungi (Fusarium oxysporum f.sp., albedinis sp, Penicelium sp., Alternaria sp. and Fusarium sp.) were studied. The inhibiting minimal concentration (CMI) effect was also given for four oils. Ten compounds were recorded jointly among the 51 identified, of which limonene (7.18 to 36.10%), β-pinene (4.35 to 30.0%) and linalool (0.21 to 63.03%) represent the principal major compounds. These results indicate that essential oils can be employed as natural fungicides against phytopathogenic fungi.Key words: GC/MS, essential oils , citrus, antifungal activity, phytopathogenic fungi
