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%), -caryophyllene (5-9%), caryophyllene oxide (7-18%) and globulol (4-6%) were the principal components. h. bivalvis gave oils in which bicyclogermacrene (20-30%), -caryophyllene (4-13%), -copaene (11-13%) and germacrene d (7-12%) were the principal components. the oils of h. nymphaeifolia from australia and fiji contained -caryophyllene (11-44%), -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 -pinene and -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.