Extracts of 40 different plant species used in the traditional medicine of the Australian Aboriginal people have been investigated for antiviral activity. The extracts have been tested for activity against one DNA virus, human cytomegalovirus (HCMV) and two RNA viruses, Ross River virus (RRV) and poliovirus type 1, at non-cytotoxic concentrations. The most active extracts were the aerial parts of Pterocaulon sphacelatum (Asteraceae) and roots of Dianella longifolia var. grandis (Liliaceae), which inhibited poliovirus at concentrations of 52 and 250 microg/ml, respectively. The extracts of Euphorbia australis (Euphorbiaceae) and Scaevola spinescens (Goodeniaceae) were the most active against HCMV. Extracts of Eremophila latrobei subsp. glabra (Myoporaceae) and Pittosporum phylliraeoides var. microcarpa (Pittosporaceae) exhibited antiviral activity against RRV.