abstract the leaf oils of the seven australian and lord howe island species of zanthoxylum have been investigated by gc and gc/ms. apart from z. ovalifolium, which had an oil yield of 1.1-1.9%, the remaining species had yields in the range trace-0.1%. the oil of z. brachyacanthum was found to be rich in -pinene (46.0%), -caryophyllene (14.0%) and bicyclogermacrene (12.5%). z. nitidum, which was sesquiterpenoid in nature, contained -caryophyllene (11.0%) and -humulene (7.2%) as principal components along with 2-tridecanone (7.7%) and an unidentified 2-alkanone (10.7%). one chemotype of z. ovalifolium contained -pinene (31.6%) and myrcene (19.8%) as major components, while the other was rich in -humulene (11.3%) and spathulenol (14.8%). in z. parviflorum, the principal components were -pinene (11.9%), -elemene (8.6%), -caryophyllene (23.4%) and caryophyllene oxide (11.7%). in z. pinnatum from lord howe island, 2-undecanone (54.3%) and 2-tridecanone (31.7%) were by far the major constituents. unlike indian oils from z. rhetsa, the australian material was sesquiterpenoid in nature with -caryophyllene (27.5%) and germacrene d (18.4%) being major components. z. veneficum oil was also sesquiterpene in nature with -caryophyllene (36.3%), germacrene d (10.9%) and bicyclogermacrene (25.4%) being the principal components.