The leaf oils of the six species of Citrus that are endemic to Australia have been investigated. C. australmica produced an oil in which the principal components were bicyclogermacrene (19-28%), germacrene-D (2-8%), 6-elemene (0.5-11%) and limonene (12-24%). C. australis oil was dominated by a-pinene (68-79%). The oil from C. garrawayi appeared to be of two forms, (1) in which the principal components were the monoterpene a-pinene (18-40%), together with P-caryophyllene (7-12%), a-hiimulene (2-17%), globulol(4-10%) and viridiflorol(4-10%), and (2) which lacked a-pinene and had P-caryophyllene (17-30%), globulol (7-10%) and viridiflorol (7-10%) as principal components. C. glauca contained a- and P-pinene(24-47% and 12-17%, respectively) and the two furanoid forms of linalool oxide (0.8-15% total) as principal components. The oil of C. grucilis contained y-terpinene(33.8%), p-cymene (14.8%). bicyclogermacrene (10.2%) and (E)-nerolidol(20.4%) as principal components, accounting for 80% ofthe oil. C. inodora gave an oil in which germacrene D (0.4-24%), germacrene B (14%) and bicyclogermacrene (0.9-19%) were the principal components.