the chemical composition of the essential oils of aerial parts and flowers of chromolaena odorata (l.) r. m. king & h. rob., collected from western ghats region, were obtained by hydrodistillation and analyzed by gas chromatography (gc) and gas chromatography/mass spectrometry (gc-ms). fifty two and thirty four compounds were identified from aerial parts and flowers, representing 94.9 % and 95.2 % of the total oils, respectively. the essential oil from aerial parts was dominated by pregeijerene (14.2 %), epi- cubebol (9.8 %), cubebol (8.6 %), cis-sabinene hydrate (5.7 %), 10-epi--eudesmol (3.8 %), germacrene-d-4- ol (3.6 %) and -cadinene (3.5 %), while germacrene d (24.8 %), geijerene (12.6 %), pregeijerene (12.5 %), cyperene (7.8 %), 10-epi--eudesmol (4.7 %), -muurolol (3.6 %) and khusimone (3.4 %) were identified as the major constituents of flowers oil of c. odorata.