Abstract The leaf oils of the three species of Hernandia occurring in Australia were investigated. All gave oil in low (trace-0.05%) yields which were almost entirely sesquiterpenic in content. Hernandia albiflora gave oils in which bicydogermacrene (trace -19%), β-caryophyllene (5-9%), caryophyllene oxide (7-18%) and globulol (4-6%) were the principal components. H. bivalvis gave oils in which bicyclogermacrene (20-30%), β-caryophyllene (4-13%), α-copaene (11-13%) and germacrene D (7-12%) were the principal components. The oils of H. nymphaeifolia from Australia and Fiji contained β-caryophyllene (11-44%), α-humulene (14-17%) and caryophyllene oxide (5-20%) as principal components. Gyrocarpus americanus subsp. americanus, from Australia, gave a leaf oil (in 0.2-0.7% yield) whose composition was more variable. In some oils the α-pinene and β-pinene content accounted for 40% while in other oils sesquiterpenes accounted for the majority of the oil, with germacrene D (31%) being the principal component. G. americanus subsp. sphenopterus gave an oil in 0.2% yield in which sesquiterpenes were the major components.