Abstract The leaf oils of the four species of Waterhousea have been investigated by GC and GC/MS. Waterhousea floribunda gave a variable oil that in most cases was dominated by Î±- and Î²-pinene (17â21%), while at the other extreme the major compounds were sesquiterpenes, with no one compound predominating. W. hedraiophylla gave an oil dominated by Sesquiterpenes with spathulenol, calamenene, Î´-cadinene and bicyclogermacrene being the principal components. W. unipunctata also gave a sesquiterpenic oil with germacrene D (8.2â25.6%), bicyclogermacrene (3.2â12.3%), globulol (0.4â15.8%) and viridiflorol (0.2â9.6%) being the principal components. Apart from containing both mono- and Sesquiterpenes, Waterhousea mulgraveana oil also contained mixtures from 1,3,5-trimethoxybenzene, 2,4,6-trimethoxyethylbenzene, 2,4,6-trimethoxystyrene and 2,4,6-trimethoxy-3,5-dirnethylstyrene.