We evaluated the ability of selected strains of the Australian mosquitoes, Aedes notoscriptus (Skuse), Ae. vigilax (Skuse), Culex annulirostris Skuse, and Cx. quinquefasciatus Say, to function as potential vectors of Rift Valley fever (RVF) virus, should that virus be introduced accidentally into Australia. After feeding on a hamster with a viremia of 107 plaque-forming units/ml of blood, Ae. notoscriptus and Cx. annulirostris were the most susceptible, with infection rates of 86 and 55%, respectively. Female Ae. vigilax and Cx. quinquefasciatus also were susceptible, with infection rates of 38 and 30%, respectively. All of these species transmitted RVF virus by bite 7–10 d after intrathoracic inoculation, and all, except Cx. quinquefasiatus (not tested), transmitted RVF virus 10–16d after oral exposure. The presence of competent mosquito vectors for RVF virus in Australia indicates the potential for RVF virus epizootics to occur should this virus be introduced into Australia.