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 a-pinene (46.0%), P-caryophyllene (14.0%) and bicyclogermacrene (12.5%). Z. nitidum, which was sesquiterpenoid in nature, contained P-caryophyllene (11 .O%> and a-humulene (7.2%) as principal components along with 2-tridecanone (7.7%) and an unidentified 2-alkanone (10.7%). One chemotype of Z. ovalifolizim contained a-pinene (31.6%) and myrcene (19.8%) as major components, while the other was rich in a-humulene (11.3%) and spathulenol(l4.8%). In Z.paruzporum, the principal components were a-pinene (11.9%), p-elemene (8.6%), P-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 0-caryophyllene (27.5%) and germacrene D (18.4%) being major components. Z. veneficum oil was also sesquiterpenic in nature with P-caryophyllene (36.3%), germacrene D (10.9%) and bicyclogermacrene (25.4%) being the principal components.