abstract the leaf oils of the australian species of xanthostemon have been examined by a combination of gc and gc/ms. xanthostemon arenarius produced an oil dominated by sesquiterpenes, with the principal components being -selinene (12-17%), -selinene (6-10%), 7-epi--selinene (7-11%), -humulene (0.3-10%, the majority > 6%) and spathulenol (3-19%). xanthostemon chrysanthus produced a leaf oil in which the principal component was the -triketone leptospermone (65-84%). the leaf oil of x. crenulatus was dominated by the sesquiterpene ketone, cyclocolorenone (65-80%) and the aromatic ketone apodophyllone (6-17%). the leaf oil of x. eucalyptoides was dominated by the aromatic ketones baeckeol methyl ether (34-41%), baeckeol (15-29%), isobaeckeol (5-8%) and apodophyllone (7-9%). the leaf oil of x. formosus was, once again, sesquiterpenoid in nature. the principal components were -caryophyllene (10-24%), -bisabolene (9-16%) and sesquiphellandrene (9-20%). xanthostemon graniticus was unusual within the genus in that it produced a monoterpenic oil, the principal component being -pinene (69.5%). xanthostemon oppositifolius gave an oil which was dominated by -triketones. the principal components were xanthostemone (1625%) and a compound considered a one carbon homologue, which is as yet unidentified (24-35%). xanthostemon paradoxus produced a leaf oil that was sesquiterpenoid in nature. the principal components were -caryophyllene (14%), spathulenol (14.9%) and globulol (8%). xanthostemon psidioides was another species whose oil was dominated by -triketones, the principal component being xanthostemone (73.1%). xanthostemon umbrosus, the species with the widest distribution in this investigation, produced a variable oil. the various oils were dominated by the sesquiterpene ketone, cyclocolorenone (77-83%), or methyl farnesoate (3257%) and farnesoic acid (9-26%) or -santalene (6-7%), isobaeckeol (30-40%) and an unknown, presumed aromatic, compound mw 252 (3-23%). the leaf oil from x. verticillatus was unusual amongst the other australian species of xanthostemon in that it contained 1,3-dimethoxy-5-isopropylbenzene as its major component (96-97%). xanthostemon whitei gave a sesquiterpenic oil which was similar to that produced by x. arenarius. xanthostemon youngii also gave a sesquiterpenic oil, the principal components being -copaene (3-13%), -caryophyllene (11-13%), aromadendrene (3-12%), and -cadinene (4-18%). xanthostemon sp. (bolt head jrc +8805) gave a terpenoid oil in which the major components were the hydrocarbons, -cadinene (18%) and calamenene (29.3%). oil yields over the range of species were 0.1-0.6%, w/w, based on fresh leaves.