In 1986-87, enzyme-linked immunosorbent assay (ELISA) was used to test for potato virus S (PVS), potato virus X PVX) and potato leafroll virus (PLRV) in certified potato "seed" obtained from either Victoria or New South Wales. one of the viruses was found in the Victorian "seed", but one out of three samples from New South Wales contained 10% PVS. In similar ELSA tests of tubers harvested from commercial crops in Queensland, PVS and PVX were found in about two-thirds of crops at an overall average level of 3-4%, whereas PLRV occurred in tubers of all crops tested at an average level of 9%. It is concluded that the level of PVS and PVX in certified "seed" and commercia1 crops in Queensland is much lower than was found in a previous survey in 1977-78, and that PLRV is now the most common virus of potatoes in Queensland.