The leaf oils of eight described and one undescribed species of Backhousia were examined by GC and GC/MS. The major components of the five suspected chemotypes of B. angustifolia F. Muell. were 1,8-cineole, (E)-β-ocimene, angustifolenone, angustifolionol, dehydroangustione and angustione. B. anisata Vickery was found to exist in two chemotypes in whch the major compound was either (E)-anethole or methyl chavicol. The oil from B. bancroftii F. M. Bailey & F. Muell., which vaned quantitatively between trees, contained octyl acetate (0.3-61.7%), dodecyl acetate (0.2-2l.O%), dodecanol (trace-22.9%), decyl acetate (0.5-39.0%), decanol (0.1-17.4%), 2,4,6-trimethoxy-3 methylacetophenone (trace-23.0%) and a novel compound, bancroftinone (6-hydroxy-2,4-dimethoxy-3-methyl acetophenone) (trace-40.0%) as its major constituents. B. citriodora F. Muell. was found to exist as two chemotypes in which either citral or citronellal predominated. The major constituents of B. hughesii C. T. White were β-bisabolene (1.0- 44.0%) and an unidentified sesquiterpene hydrocarbon (8.0-54.0%). B. kingii Guymer gave an oil which contained a-pinene (24.0-49.0%), limonene (7.0-24.0%) and 1,8-cineole (10.0-17.0%) as the principal constituents. Four chemotypes of B. myrtifolia Hooker & Harvey were found in which the major components were methyl eugenol, (E)-methyl isoeugenol, elemicin and (E)-isoelemicin. B. sciadophora F. Muell. gave an oil with a-pinene (44.0-55.0%), β-pinene (2.4-8.0%), limonene (6.5-12.7%) and linalool (2.8- 6.7%) as its major components. The principal components of Backhousia sp. (Didcot P.I. Forster PIF12671) were a-pinene (11.0%), β-pinene (5.3%), β-caryophyllene (12.0%), dodecyl acetate (8.1%) and dodecanol(8.2%).