High antioxidant capacities have been linked with a reduction in the incidence of chronic diseases including cardiovascular disease, diabetes, obesity, neurodegeneration, inflammation and cancer. Furthermore, phenolic antioxidants may not only have protective effects against these diseases, but may also have therapeutic potential in reversing them by modulation of the cellular redox state. Thus, plants with high antioxidant capacities have potential in the development of new chemotherapeutic treatments to prevent and treat some cancers. Several native Australian plant species including Terminalia ferdinandiana Exell (Kakadu plum), Tasmannia lanceolata (Poir.) A.C.Sm., (Tasmannian pepper), Syzygium australe (H.L.Wendl. ex Link) B.Hyland (brush cherry), Syzygium luehmannii (F.Muell.) L.A.S.Johnson (riberry), Davidsonia pruriens F.Muell. (Davidson’s plum), Elaeocarpus angustifolius Blume (quandong), Kunzea pomifera F.Muell. (muntries), Podocarpus elatus R.Br.ex Endl., (Illawarra plum) and Acronychia acidula F.Muell., (lemon aspen) have recently been reported to have extraordinarily high antioxidant content and were therefore selected to screen for the ability to inhibit proliferation of selected carcinoma cell lines.