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 1.1â1.9%, the remaining species had yields in the range trace-0.1%. The oil of Z. brachyacanthum was found to be rich in α-pinene (46.0%), β-caryophyllene (14.0%) and bicyclogermacrene (12.5%). Z. nitidum, which was sesquiterpenoid in nature, contained β-caryophyllene (11.0%) and α-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 α-pinene (31.6%) and myrcene (19.8%) as major components, while the other was rich in α-humulene (11.3%) and spathulenol (14.8%). In Z. parviflorum, the principal components were α-pinene (11.9%), β-elemene (8.6%), β-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 β-caryophyllene (27.5%) and germacrene D (18.4%) being major components. Z. veneficum oil was also sesquiterpene in nature with β-caryophyllene (36.3%), germacrene D (10.9%) and bicyclogermacrene (25.4%) being the principal components.