abstract a water-distilled oil obtained from the aerial parts of xanthium brasilicum vellozo was analyzed by gc/ms. the oil consisted mainly of monoterpenes and a small percentage of sesquiterpenes. fifteen compounds were identified, of which borneol (28.9%), fenchone (21.1%) and isobornyl acetate (9.1%) were the major constituents. key word index: xanthium brasilicum compositaeessential oil compositionborneolfenchone