Abstract The essential oil isolated from the leaves and ï¬owers of Ageratum conyzoides L. were analysed by GC and GCâMS. The oil contained ageratochromene (precocene II, 25.89%); the sesquiterpene Î² âcaryophyllene (23.79%); demethoxyageratochromene (precocene I, 14.76%) and some monoterpene hydrocarbons, with percentages of 2â5.5%. Comparative analysis with data from Cameroon, Ghana and Vietnam is also reported. Copyright Â© 2003 John Wiley &amp; Sons, Ltd.