the hydrodistilled essential oil of the roots of chromolaena odorata (l.) r. m. king & h. rob. was analysed by gas chromatography equipped with flame ionization detector (gc-fid) and gas chromatography coupled with mass spectrometry (gc/ms). a total of twenty-nine compounds have been identified, accounting 97.6% of the total oil. the main constituents were himachalol (24.2%), 7-isopropyl-1,4-dimethyl-2-azulenol (17.6%), androencecalinol (14.1%), and 2-methoxy-6-(1-methoxy-2-propenyl) naphthalene (5.6%). the essential oil consists mainly of phenyl derivatives (41.6%), followed by oxygenated sesquiterpenes ((26.6%), long-chain hydrocarbons (18.9%), sesquiterpene hydrocarbons (6.8%), oxygenated monoterpenes (2.8%), and monoterpene hydrocarbons (0.9%). this study revealed that the roots of c. odorata produced different chemotypes other than leaves oil. this is the first report on the essential oil composition of the roots of c. odorata .