The defensive secretions of 88 species of Australian Tenebrionidae from 63 genera and 23 tribes have been analysed. These secretions comprise mainly quinones with I-alkenes and, in some cases, smaller quantities of other components. In general, the results support the conclusion from overseas studies that defensive chemistry in this family has been plastic and that individual components are seldom likely to prove characteristic for particular taxa. However, limited correlations between defensive chemistry and taxonomy are apparent and their bearing on some recent changes in higher classification of the Australian fauna is discussed.