the chemical composition of the hydro-distilled essential oils of leaf, flower, stem and root of ageratum conyzoides l. were analyzed by gas chromatography equipped with flame ionization detector (gc-fid) and gas chromatography coupled with mass spectrometry (gc-ms). a total of 42 constituents have been identified accounting 99.0 % (leaf), 97.3 % (stem), 98.3 % (flower) and 96.6 % (root) of the volatile compounds. the major constituents were 6-demethoxy-ageratochromene (precocene i) and -caryophyllene dominated in leaf (72.3 %; 12.1 %), stem (66.5 %; 10.2 %), flower (50.3 %; 14.6 %) and root (79.3 %; 6.0 %) essential oils. the compound ageratochromene (precocene ii) was found relatively high amount in flower (10.5 %) than leaf (3.1 %), root (0.4 %) and stem (0.3 %) oils. the occurrence of androencecalinol is being reported for the first time in leaf, flower, stem and root oils in low quantity (0.7 - 0.3 %).