In laboratory studies, Culex sitiens was found to be moderately susceptible to infection by Ross River (RR) virus with a TC ID50 estimated at 107.3/mosquito. Evidence of infection was found 4 d after ingestion of virus and mosquitoes were still infective at 18 d. The virus was transmitted to day-old chickens from 4 d (10%) but maximum rates of transmission (33.3%) were reached 11–14 d after ingestion. Newly-hatched larvae were fed both high (12.6 mg) and low (4.2 mg) diets and fed on 5–25% sucrose as adults. Only 4 out of 485 females fed on the high diet and 0 of 247 on the low diet, developed mature ova suggesting that autogeny is probably uncommon in nature. These studies suggest that Cx. sitiens may only play a limited role in the natural transmission of RR virus.