the chemical composition of the essential oils isolated from the aerial parts of senecio vulgaris plants collected in 30 corsican localities was characterized using gc-fid and gc/ms analyses. altogether, 54 components, which accounted for 95.2% of the total oil composition, were identified in the 30 essential-oil samples. the main compounds were -humulene (1; 57.3%), (e)--caryophyllene (2; 5.6%), terpinolene (3; 5.3%), ar-curcumene (4; 4.3%), and geranyl linalool (5; 3.4%). the chemical composition of the essential oils obtained from separate organs and during the complete vegetative cycle of the plants were also studied, to gain more knowledge about the plant ecology. the production of monoterpene hydrocarbons, especially terpinolene, seems to be implicated in the plant-flowering process and, indirectly, in the dispersal of this weed species. comparison of the present results with the literature highlighted the originality of the corsican s. vulgaris essential oils and indicated that -humulene might be used as taxonomical marker for the future classification of the senecio genus. a study of the chemical variability of the 30 s. vulgaris essential oils using statistical analysis allowed the discrimination of two main clusters according to the soil nature of the sample locations. these results confirmed that there is a relation between the soil nature, the chemical composition of the essential oils, and morphological plant characteristics. moreover, they are of interest for commercial producers of essential oil in selecting the most appropriate plants.