abstract the essential oils of three australian species of the genus cassytha have been investigated using gc and gc/ms. cassytha filiformis produced an oil that was sesquiterpenoid in nature, with bicyclogermacrene (12-26%), spathulenol (27-36%) and -caryophyllene (5-10%) being the principal components. cassytha pubescens appeared to exist in several chemical types. a principal components analysis of the oils appeared to indicate that there were three chemical types present in the 13 collections. the first variety contained (e)-nerolidol (26.7%) and -caryophyllene (23.5%) as major components. the second chemical variety of this species showed elevated levels of -copaene (4-6%), moderate amounts of -caryophyllene (8-14%), caryophyllene oxide (3-17%) and bicyclogermacrene (2-9%), and high levels of spathulenol (27-32%). the third variety was more variable and contained significant amounts of spathulenol (4-21%), bicyclogermacrene (2-40%), -caryophyllene (1-31%), and aromadendrene (0.7-10%). the principal component of c. capillaris oil was spathulenol (31%). the oil yields, in all species, were 0.1% or less.