The volatile oil from Vernonia anthelmintica Willd was analyzed by GC/MS/DS and twenty four principal components èonstituting 91.42% of the oil were identified, namely; ethyl acetate, 2-ethoxy-butane 、ethyl buthyl ether 、2-methyl propanoic acid、1.2-dimethyl imidazole、ethyl benzene、4-carene、camphene、benzaldehyde、β-pinene、2-carene、bornylene、phenylacetaldehyde、sabinene、isolimonene、α-terpineol、terpineol-4、α-terpineol、carvone、anise camphor、isocaryophy l1ene、caryophyllene、silinene and 4-methyl-phenyl phenyl ether.

Key words: component analysis, mass-spectrography, gas chromatography