A detailed investigation of the wood, leaf, branch and root oil of Eremophila mitchellii (Benth.) was carried out by a combination of GC-FID, GC-MS and NMR. The wood oil was composed predominantly of eremophilanes, a rare class of biologically active, bicyclic sesquiterpenoids. The root oil was also found to contain the eremophilanes together with the zizaene sesquiterpene, sesquithuriferone. 9-Hydroxy-1,7(11),9-eremophilatrien-8-one and the known 1(10),11-eremophiladien-9-one (eremophilone), 9-hydroxy-7(11),9-eremophiladien-8-one (2-hydroxyeremophilone), 8-hydroxy-11-eremophilen-9-one (santalcamphor), 8-hydroxy-10,11-eremophiladien-9-one, sesquithuriferone and 8-hydroxy-1,11-eremophiladien-9-one were purified and elucidated by NMR. Three approaches to the purification of the major eremophilanes from the wood oil are described. (+) Spathulenol, α-pinene, globulol, viridiflorene were the major constituents of the leaf oil. All of the essential oils and the eremophilanes exhibited cytotoxicity against P388D(1) mouse lymphoblast cells in-vitro.